CHAPTER

Chemistry of
17 Lighter Elements
Chapter Highlights
Sodium (Occurrence, Extraction, Properties, Uses) and its compounds like NaCl, Na2CO3, NaHCO3, NaOH.
Potassium (Occurrence, Extraction, Properties, Uses) and its compounds like KCl, KOH. Magnesium (Occurrence,
Extraction, Properties, Uses) its compounds like MgCl2, MgSO4. Calcium (Occurrence, Extraction, Properties,
Uses) and its compounds like CaO, Ca(OH)2, CaCO3, CaSO4, Plaster of Paris, Bleaching powder. Aluminium
(Occurrence, Extraction, Properties, Uses) and its compounds like AlCl3, Alums, Cement and Biological role of
Na, K, Mg and Ca and various levels of multiple-choice questions.

SODIUM, POTASSIUM, MAGNESIUM, CALCIUM, ALUMINIUM

–
SODIUM (11NA23) 
NaCl ↽  Na+ + Cl
⇀
At cathode (Iron rod):
Occurrence
• Sodium is present in earth crust as sodium alumino‑ Na+ + e– Na
silicates (2.27%). At anode (Graphic rod):
• The most common compound of sodium is NaCl, 2Cl–‑ + 2e– Cl2 + 2e–
that is rock salt or lake salt and it has FCC unit cell
structure. The coordination number is 6 for both Na+ Castner process
and Cl–. Here electrolysis of NaOH is carried out at 330oC using
• Important compounds of sodium are: iron cathode and nickel anode
Soda feldspar Na2OAl2O3.6SiO2 
2NaOH ↽⇀
 2Na+ + 2OH –
Cryolite Na3AlF6 At cathode:
Chile sal petre NaNO3 2Na+ + 2e– 2Na(s)
Glauber’s salt Na2SO4.10H2O
Borax Na2B4O7.10H2O At anode:
• It was isolated by Davey by the electrolysis of fused 4OH– 2H2O + O2 + 4e–
NaOH. During electrolysis, oxygen and water are produced.
Water formed at the anode gets partly evaporated and is
Preparation of Sodium partly broken down. Whereas, the hydrogen is discharged
Down’s method at cathode.
• Sodium is obtained by electrolysis of fused NaCl. H2O ↽  H+ + OH–
⇀
• Here, CaCl2 + KF lowers the melting point of NaCl At cathode:
2H+ + 2e– 2H H2 ↑
[800oC to 600oC]
17.2 Chapter 17

NaH • Basic nature It reacts with acid or acidic oxide to

NaNH2 Na2O give salts.
H2O NaOH + HNO3 NaNO3 + H2O
NH3 H2 O2 • Reactions with metals
Group IA metal + NaOH No reaction
Sodium NaOH Other metals + NaOH Na2MO2 + H2↑
(Na) Sodium metalate

CO2 M may be Zn, Sn, Pb, Be

• Reactions with non-metals
Na2S O2 Na2CO3 1. Reaction with boron
2B + 6NaOH 2Na3BO3 + 3H2
Sodium borate
Na2O2
Na2SO3+I2 C6H5COCl CO or CO2 2. Reaction with silicon
H2SO4 2NaOH + Si + H2O Na2SiO3 + 2H2
Sodium silicate
Na2S2O3 (C6H5CO)2O2 3. Reaction with white phosphorous
Hypo Benzoyl
peroxide P4 + 3NaOH + 3H2O 3NaH2PO2 + PH3
Na2SO4 Sodium hypophosphite
4. Reaction with sulphur
Figure 17.1 Summary of Important Rection of Sodium
4S + 6NaOH Na2S2O3 + 2Na2S + 3H2O
Hypo
Compounds of sodium 5. Reaction with halogens
Caustic soda or sodium hydroxide (NaOH) 2NaOH + X2 NaXO + NaX + H2O
Dil. and cold Sodium hypohalite
Preparation of sodium hydroxide
6NaOH + 3X2 5NaX + NaXO3 + 3H2O
Gossage or causticization method Hot and conc. Sodium halate
Na2CO3(aq) + Ca(OH)2(aq) 2NaOH(aq) + CaCO3 • Reactions with salts
FeCl3
Lowing’s method NaOH Fe (OH)3
Fusion (Red‑brown precipitate)
Na2CO3 + Fe2O3 2NaFeO2
– CO2↑ HgCl2
H2O NaOH Hg(OH)2
2NaFeO2 2NaOH + Fe2O3
Δ
Δ
Electrolysis of brine solution [aqueous NaCl] H2O + HgO↓
Yellow
• For the electrolysis of aqueous NaCl, electrolytic cells NaOH
AgNO3
AgOH Δ Ag2O↓
like Nelson, Constner‑Kelner and Solvay cells are used. Brown
• Here NaOH, Cl2, H2 are formed. NaOH
AlCl3
Al (OH)3 Na NaAlO2
• The following reactions occur: Sodium
metaaluminate
NaCl ↽  Na+ + Cl–
⇀
When NaOH is added to the given metallic com‑
H2O ↽ H+ + OH–
 ⇀
pounds, their sodium metalates are formed.
At anode:
– SnCl2 + 2NaOH Sn (OH)2
2Cl Cl2 + 2e–
or ZnCl2 or Zn (OH)2
At cathode:
or Pb(NO3)2 or Pb (OH)2
2Na+ + 2e– 2Na
2Na + 2H.OH 2NaOH + H2↑ 2NaOH

Properties of NaOH Na2SnO2 + 2H2O

or Na2ZnO2 or Na2PbO2
• It is a white crystalline, deliquescent, soapy solid
with a melting point of 180oC.
 Chemistry of Lighter Elements 17.3

• On reacting with ammonium salts, it liberates ammonia. Sodium Bicarbonate or Baking Stoda
NH4Cl + NaOH Δ
NH3 ↑ + HCl (NaHCO3)
• Formation of HCOOH • It is prepared as follows:
150oC–200oC Na2CO3 + CO2 + H2O 2NaHCO3
NaOH + CO 5–10 atm P HCOONa
• NaHCO3 gives yellow colour with methyl red or
H.OH methyl orange but no colour with HPH that is
phenolphthalene.
HCOOH
• It is a white crystalline solid, partially soluble in
Uses of NaOH water. Its aqueous solution is basic.
• In hydrolysis of ester and saponification. • It is used to cure acidity in stomach and is used in
• In refining of bauxite (by Baeyer’s method). the making of baking powder (sodium bicarbonate +
• In the synthesis of hydrogen (Uyeno method) potassium hydrogen tartarate).
Sodium carbonate or washing soda Na2CO3.
2Al + 2NaOH + 2H2O 2NaAlO2 + 3H2↑
10H2O Na2CO3 is termed as soda‑ash while Na2CO3.
Sodium chloride (NaCl) H2O is called crystal carbonate.

• It is called common salt or rock salt or sea salt or Methods of preparation

tablesalt. • It is prepared by Leblanc process. Here, the raw
• Sea water contains nearly 2.95% NaCl. material used to prepare Na2CO3 are NaCl, CaCO3,
coke and H2SO4
• 28% aqueous NaCl solution is called brine.
2NaCl + H2SO4 Na2SO4 + 2HCl
Preparations of Sodium chloride: It is mainly manu‑ Salt cake
factured from sea water by evaporation under the heat of Na2SO4 + 4C Na2S + 4CO↑
the sun. As it contains impurities of MgCl2, CaCl2, CaSO4, Black salt
so it is further purified by passing HCl gas, where due to Na2S + CaCO3 Na2CO3 + CaS
Black ash
common ion effect pure NaCl gets precipitated.
• This method is used to prepare washing soda, salt
Properties of Sodium chloride cake, black salt and black ash.
• It is a white crystalline solid which is hygroscopic in Solvay ammonia soda process Na2CO3 is industrially
nature. prepared by Solvay method using NaCl, CaCO3 and
• It dissolves in water and the process of dissolution is NH3 as follows:
endothermic. NH3 + H2O + CO2 NH4HCO3
NaCl
NaOH NH4HCO3 aq. NaHCO3 + NH4Cl
Δ
2NaHCO3 Na2CO3 + H2O + CO2↑
above 100oC
Cl2 and H2 by product
Electrolysis of aq. solution • Here Na2CO3, NaHCO3, CaCl2 are obtained as by‑
products.
Common Salt (NaCl) • NaHCO3 is precipitated owing to its low solubility
NH3+ CO2 Leblranc process for the product value.
Solvay process manufacture of Na2CO3 • Since KHCO3 cannot be precipitated due to its high
H2SO4 solubility product value, so it cannot be prepared by
Electrolysis of fused NaCl this method.
having CaCl2 + KF Properties of sodium carbonate
NaHCO3 Na2SO3 + HCl
Sodium metal • It is a white crystalline solid, partially soluble in
C water and its aqueous solution is basic.
• Efflorescence
Air
Na2S Na2CO3.10H2O Na2CO3.H2O + 9H2O
Powder form
Figure 17.2 Summary of Some Important Reactions (loss of weight)
17.4 Chapter 17

• Effect of heating Modern method

Na2CO3.10H2O Na2CO3 Here potassium is obtained by the reduction of molten
–10H2O
KCl with metallic sodium in a stainless steel vessel at
strong
1120K–1150K.
∆
1120K–1150K
XXX KCl (1) + Na (g) NaCl + K (g)
(No dissociation)
• Potassium forms following oxides:
• Reaction with lead acetate K2O (Potassium monoxide)
3(CH3COO)2 Pb + 3Na2CO3 + H2O 2PbCO3Pb(OH)2 KO2 (Potassium superoxide)
Basic lead carbonate K2O3 (Potassium sesquioxide)
+CO2 +6CH3COONa
Compounds of Potassium
• Reaction with copper sulphate
Potassium hydroxide (KOH)
2CuSO4 + 2Na2CO3 + H2O Cu(OH)2.CuCO3 +
Basic copper carbonate • It is mainly obtained by the electrolysis of an aque‑
CO2 + Na2SO4 ous solution of KCl just like the process followed for
NaOH.
• Reaction with silica
• It is also obtained by the action of soda lime on
Na2CO3 + SiO2 Na2SiO3 + CO2↑ potassium carbonate.
• It is used for softening hard water, refining of petrol • Its aqueous solution is known as potash lye.
and in the manufacture of glass and borax. • It is used for the absorption of gases like CO2, SO2.
• Na2CO3 + K2CO3 is a fusion mixture. • Alcoholic KOH is used as a dehydrating agent for the
• Na2CO3 gives pink colour with HPH, yellow colour dehydration of alkyl halides in organic chemistry.
with MeOH or methyl red and blue colour with red
litmus. Potassium chloride (KCl) It occurs as sylvine (KCl) and
as carnalite (KCl.MgCl2.6H2O).
POTASSIUM (19K39) Preparation of potassium chloride
From sylvine (KCl) Sylvine is a mixture of KCl and NaCl.
Occurrence
When the boiling hot saturated solution of the mixed salts
Potassium is present in combined state in nature. The main in water is cooled, KCl separates out and NaCl is left
minerals of potassium are: behind in the solution.
• Carnalite KCl.MgCl2.6H2O From carnalite (KCl.MgCl2.6H2O) It is always found
• Feldspar K2O.Al2O3.6SiO2 (clay) mixed with NaCl and MgSO4. To remove NaCl and MgSO4,
the ore is grounded and extracted with hot 20% solution of
• Kainite KCl.MgSO4.MgCl2.3H2O
MgCl2. Carnalite dissolves while NaCl and MgSO4 remain
• Sylvine KCl undissolved. These are filtered off and the solution which
• Polyhalite K2SO4.MgSO4.CaSO4.6H2O contains only carnalite is crystallized so that cubic crystals
• Indian Saltpetre KNO3 of KCl separate out, leaving behind MgCl2 in the solution.

Extraction of Potassium Properties of potassium chloride

• It is a colourless crystalline solid having cubic
Potassium is not obtained by the electrolysis of fused KCl,
crystals.
as potassium has a lower boiling point (1039 K) than the
melting point of KCl (1063 K) and hence it vapourizes. • Its melting point and boiling point are 768oC and
Therefore, potassium metal is extracted by using following 1411oC respectively.
methods: • It is extremely soluble in water and closely resembles
NaCl in most of its properties, except that its solu‑
By the electrolysis of fused KOH bility increases rapidly with the temperature and is
Here the reactions involved are as follows: more readily fusible.
KOH K+ + OH– Uses of potassium chloride
At cathode: K+ + e– K • It is used in the manufacture of potassium and its
–
At anode: 4OH 2H2O + O2 + 4e– compounds.
 Chemistry of Lighter Elements 17.5

• It is used as a potassium fertilizer (K‑type fertilizer) • It react with halides to from Grignard reagent which
since it supplies potassium (as K2O) to the soil. is used in various organic synthesis.
Ethers
RX + Mg R–Mg–X
MAGNESIUM (12Mg24) Grignard reagent

Occurrence
Magnesium is present in the form of ores as in:
FA C T TO R E M E M B E R
Magnesite (MgCO3)  Mg-fire cannot be extinguished by CO2.
Dolomite (MgCO3.CaCO3)  Mg is refined by subliming at 600oC and 1 mm Hg
Kieserite (MgSO4.H2O) pressure.
Asbestos [CaMg3 (SiO3)4]  Being more electropositive, magnesium prevents ships,
pipes from corrosion.
Extraction of Magnesium

By the electrolysis of anhydrous MgCl2 or MgO Uses of Magnesium

It is extracted by the electrolysis of fused MgO or anhy‑ • Magnalium (15% Mg + 85%–99% Al) is used in
drous MgCl2 which are obtained from carnalite and mag‑ making parts of aeroplanes and motors.
nesite. • Electron metal (95% Mg, 4.5% Zn, 0.5% Cu) is used
in the manufacture of air crafts.
• Here NaCl is added to decrease the melting point and
to prevent hydrolysis. • Mg is used in the extraction of B, Si, Ti.
• In Dow’s method, MgCl2 is obtained from sea water. • Mg is used as a deoxidizer for Cu, steel.
• On electrolysis, Mg is discharged at cathode.
Compounds of Magnesium
By thermal reduction of MgO Magnesia (MgO) It is prepared by heating the following:
It is carried out at 2000oC in vacuum by reducing agent Δ
Mg(OH)2 MgO + H2O
likes C or Si or Al. Δ
MgCO3 MgO + CO2
MgO + C Mg + CO 2Mg(NO3)2
Δ
2MgO + 4NO2
2MgO + Si 2Mg + SiO2 Δ
2Mg (s) + O2 2MgO(s)
3MgO + 2Al 3Mg + Al2O3 Strong
MgCl2.6H2O MgO(s)
heating
Properties of Magnesium Properties and uses of magnesia
• Magnesium is a hard malleable, ductile, silvery white • It is an amorphous powder and is slightly soluble in
metal. water.
• Mg burns in N2, O2, CO2, SO2. MgO + H2O Mg(OH)2
Δ
2Mg + O2 2MgO • It is a basic oxide so it forms salts with acids.
White dazzling light so it is
used in flash light for photography MgO + H2SO4 MgSO4 + H2O
2Mg + CO2 Δ 2MgO + C • It is used in medicine as an antacid.
Carbon black • It is also used in making soral cement.
(proves CO2 has C)
• Mg dissolves in dilute acids with the removal of H2. Magnesium Chloride (MgCl2)
Mg + H2SO4 MgSO4 + H2
• It occurs as carnalite (KCl.MgCl2.6H2O).
• Magnesium acts as a strong reducing agent.
• It is extracted from carnalite as
B2O3 + 3Mg 3MgO + 2B MgCl2 + 6H2O MgCl2.6H2O
Δ In vacuum
3Mg + KClO3 Burns with explosion KCl + 3MgO
17.6 Chapter 17

Properties and uses of magnesium chloride • In mineral form it is present as:

• It is a colourless, crystalline, deliquescent solid CaCO3 limestone, marble, chalk or
which is highly soluble in water. calcite
• It is used for preparing many magnesium compounds CaSO4.2H2O gypsum
like Mg(OH)2, MgO, MgCO3. CaCO3.MgCO3 dolomite
• MgCl2.5MgO.xH2O is soral magnesia, a cement CaF2 fluorspar
used in dental filling. Ca3(PO4)2 phosphorite
3Ca3(PO4)2.Ca(OH)2 hydroxyapatite
Magnesium Sulphate or Epsom Salt or
Epsomite Extraction of Calcium
[MgSO4.7H2O] • Calcium is obtained by electrolysis of CaCl2. CaF2 is
Preparation of magnesium sulphate It is prepared from added to decrease its melting point.
magnesite or dolomite ores by reacting them with dilute 700°C
CaCl2 Ca + Cl2
H2SO4 as shown: Cathode

MgCO3 + H2SO4 MgSO4 + H2O + CO2 At cathode: Ca2+ + 2e Ca

–
MgCO3.CaCO3 + 2H2SO4 MgSO4 + CaSO4 + At anode: 2Cl Cl2 + 2e
2CO2 + 2H2O • It is removed by screw rearrangement.
Properties of magnesium sulphate • Thermite or Gold Schmidt method
• It is a colourless crystalline solid which is soluble in 3CaO + 2Al Ca + Al2O3
water. It is isomorphous with ZnSO4.7H2O.
• Effect of Heating Properties of Calcium
MgSO4 .7H2O 150°C MgSO4.H2O • Calcium is a silvery white, malleable and ductile
–6H2O metal with a specific gravity of 1.5.
MgSO4 .H2O MgSO4 + H2O O2
200°C 2Ca 2CaO
Kieserite
N2
3Ca Ca3N2
Uses of magnesium sulphate H2
Ca CaH2
• It is used as a purgative (medicine). It also finds Hydrolith
application in dying and tanning as well as in the 2C
Ca CaC2
preparation of ceremic cement. 6NH3 Δ
Ca Ca(NH3)6 Ca(NH2)2
• Mg(ClO4)2 is anhydrous magnesium perchlorate, is Calcium
used as a dehydrating agent. amide

• (MgCO3)x, [Mg(OH)2].3H2O (Magnesium alba) is

Uses of Calcium
used in tooth powder as an antacid and laxative.
• Calcium is used as a drying agent when used in the
FA C T TO R E M E M B E R preparation of absolute alcohol.
• It is also used in the preparation of CaH2 and metallic
 Magnesia mixture is a solution of MgCl2 and NH4Cl in vanadium.
ammonia which is used to detect phosphate or arsenate • Calcium is used in metal casting as a deoxidant.
ions.
• Calcium is used as a chemical mean to remove traces
 Fluid magnesia is a solution in 100 cc of water having
of gases from vacuum tube.
12 g MgCO3 and dissolved CO2.

Compounds of Calcium
CALCIUM (20Ca40)
Calcium oxide or quick-lime (CaO)
Occurrence • It is also referred to as simply lime or burnt lime.
Ca3(PO4)2 is present in bones and teeth, while CaCO3 is • It is prepared by the following method:
present in protective shells of marine animals.
 Chemistry of Lighter Elements 17.7

Δ H2O Calcium sulphate dihydrate or gypsum (CaSO4.2H2O)

CaCO3 CaO Ca(OH)2
1000 C O Naturally occurring calcium sulphate is called alabaster.
Slaked lime
–CO2↑
[slaking of lime] Preparation of calcium sulphate dihydrate
• [Ca(OH)2 + H2O] is milk of lime. CaCl2 + H2SO4 CaSO4 + 2HCl
H2O CaCl2 + Na2SO4 CaSO4 + 2NaCl
CaO Ca(OH)2
CaO
3C
CaC2 + CO↑ Properties of calcium sulphate dihydrate
3000oC
Calcium carbide • It is a white crystalline solid which is partially
soluble in water and its dissolution in water is
H2O N2(Δ)
exothermic.
• On heating, gypsum gives plaster of paris (calcium
C2H2 + Ca (OH)2 CaCN2 + C sulphate hemihydrate). Plaster of paris when mixed
Nitrolim (fertilizer) with water, gives a hard mass.
Uses of calcium oxide • Gypsum on heating at 200oC, gives anhydrous cal‑
• It is used in the manufacture of glass, cement, bleach‑ cium sulphate known as dead burnt plaster.
ing powder, soda‑lime. 2CaSO4 .2H2O
120oC
(CaSO4)2 H2O + 3H2O
• It is used as a basic flux. Setting (ΔH = –ve ) Plaster of paris
• It is used as a drying agent (NH3, C2H5OH).
Δ 200oC
• In the refining of sugar.
Calcium hydroxide or slacked lime Ca(OH)2 It is also
2CaSO4 + H2O
called lime water.
Dead burnt
Preparation of calcium hydroxide Plaster

CaO + H2O Ca(OH)2 + Heat Uses of calcium sulphate dihydrate

• Gypsum is used in the manufacture of plaster of
Properties of calcium hydroxide
paris, cement and black board chalk.
CO2
Ca(OH)2(aq) CaCO3 + H2O • Plaster of paris is used to plaster broken bones, mak‑
or Ca(HCO3)2 ing statues, toys and chalks.
(If CO2 is in excess)
Cl2 Bleaching powder CaOCl2 or Ca(OCl)Cl It is also
Ca(OH)2 30OC CaOCl2
known as calcium chloro hypochlorite or chloride of
Bleaching Powder
Cl2 red hot lime.
Ca(OH)2 CaCl2
NH4Cl Preparation of bleaching powder It is prepared by passing
Ca(OH)2 CaCl2 + NH3 current on chlorine over dry slaked lime. The methods used
2Ca(OH)2 + 2Cl2 CaCl2 + 2H2O + Ca(ClO)2 are Bachmann method and Hasenclever method.
dil. and cold Calcium hypochlorite
Ca(OH)2 + Cl2 CaOCl2 + H2O
6Ca(OH)2 + 6Cl2 5CaCl2 + 6H2O + Ca(ClO3)2 Bleaching powder
Conc. and hot Calcium chlorate
Properties of bleaching powder
• It is used in softening of water, purification of coal
gas, and sugar. • It is mixture of calcium hypochlorite (CaOCl2.4H2O)
and basic calcium chloride (CaCl2.Ca(OH)2.4H2O)
Calcium oxide or marble or limestone (CaCO3) • It is an oxidizing agent and a bleaching agent.
Preparation of calcium oxide • Cl2 (available chlorine) is generally obtained in less
Ca(OH)2 + CO2 CaCO3 + H2O amount (35%–40%) from bleaching powder by using
CO2.
CaCl2 + Na2CO3 CaCO3 + 2NaCl
CaOCl2 + CO2 CaCO3 + Cl2↑
Uses of calcium oxide It is used in preparation of cement,
washing soda (NaHCO3 by Solvay method).
17.8 Chapter 17

• CoCl2 acts as a catalyst to decompose bleaching Roasted ore Caustic soda solution
powder to liberate oxygen High pressure (150oC, 80 atm)
CoCl2 filtered3 Fe2O3 as residue
2CaOCl2 2CaCl2 + O2↑
Filtered CO2
Uses of bleaching powder Filtrate (sodium allminate)
• It is used to purify water, to prepare CHCl3 and as a
germicide. Heat pure Al2O3
Al (OH)3
• It is used for bleaching cotton and wood pulp.
Al2O3.2H2O + 2NaOH 2NaAlO2 + 3H2O
Bauxite Sodium
ALUMINIUM (9Al27) metaaluminate
NaAlO2 + 2H2O Al(OH)3 ↓ + NaOH
Occurrence
1473 K
• Aluminium is the most abundant metal but is the third 2Al(OH)3 Al2O3 + 3H2O
Alumina
most abundant element in the earth crust (O, Si, Al, Fe).
• Some important ores of aluminium are: Hall’s process
Alunite or alum stone K2SO4.Al2(SO4)3.4Al(OH)3 +Na2CO3
Bauxite Al2O3.2H2O Bauxite (finely powdered)
Fused, extracted with water
Corundum Al2O3 Residue Fe2O3
Cyrolite Na3AlF6 CO2
Diaspore Al2O3.H2O solution
o
50–60 C and filtered
Feldspar KAlSi3O8 filtrate (Na2CO3)
Kaolinite Al2O3.2SiO2.2H2O
Mica K2O.3Al2O3.6SiO2.2H2O ∆
Precipitate Al(OH)3 Pure Al2O3
Extraction of Aluminium
• Aluminium is extracted mainly from bauxite Al2O3.2H2O + Na2CO3 2NaAlO2 + CO2 + 2H2O
(Al2O3.2H2O). 323 K–333 K
2NaAlO2 + 3H2O + CO2 2Al(OH)3 ↓
• By the purification of bauxite, Al2O3 (alumina) is
+ Na2CO3
obtained.
Al2O3, cryolite and fluorspar are mixed in the ratio Serpeck’s process
1 : 2 : 1 to form a molten mixture from which alu‑
Coke + N2
minium is recovered. Bauxite (finely powdered)
Heated to 1800oC
• For the electrolysis of Al2O3, cryolite is used to
Hydrolysis
(a) lower melting point of Al2O3 (from 2050oC to
Silica reduced + alumina form
950oC)
to Si which aluminium nitride
(b) increase conductivity of Al2O3 and to dissolve
volatalizes (AIN)
Al2O3.
• Al is collected at cathode and it is purified by Hoopes Heated
method. Al (OH)3 pure Al2O3
The various processes involved in the metallurgy of
2000 K
aluminium inlcude: Al2O3.2H2O + N2 + 3C 2AlN + 3CO ↑
+ 2H2O
Bayer process SiO2 + 2C Si ↑ + 2CO ↑
Bauxite (fine powered) FeO Fe2O3 Roasted ore
AlN + 3H2O Al(OH)3 ↓ + NH3
 Chemistry of Lighter Elements 17.9

Electrolysis of fused alumina • LiAlH4 is used as a reducing agent.

(Hall and Heroult’s method) • A mixture of aluminium powder and aluminium
• Pure alumina is mixed with a molten mixture of cryo‑ nitrate is called ammonal (an explosive).
lite (Na3AlF6) and fluorspar (CaF2) for electrolysis.
• Here the molten mixture is used to decrease the melt‑ Some Important Alloys of Aluminium
ing point of alumina. 1. Magnalium: It is an alloy of 90% Al and 10% Mg. It

Na3AlF6↽⇀
 3NaF + AlF3 is used in making balance beams.
AlF ↽ Al3+ + 3F–
 ⇀ 2. Duralumin: It is an alloy of aluminium (95.5%), cop‑
3
per (4%), magnesium (0.5%) and manganese (0.5%).
At cathode: Al3+ + 3e– Al It is used in making aeroplanes parts.
– –
At anode: F e +F 3. Alnico: It is an alloy of steel (77%), nickel (2%), alu‑
2Al2O3 + 12F 4AlF3 + 3O2 minium (20%) and cobalt (1%). It is used in making
2C + O2 2CO permanent magnets.
2CO + O2 2CO2 4. Aluminium bronze: It is an alloy of 90% copper and
10% aluminium. It is used in making coins, trays and
Properties of Aluminium picture frames.
• Aluminium is a bluish white metal with a melting (a) Some stones containing aluminium
point of 660oC and a boiling of 1800oC Ruby (red) Al2O3 + Cr
4Al 3O2
2Al2O3 Topaz (yellow) Fluorosilicate of Al
N2 Sapphire (blue Lapis Lazule) Na–Al silicate
2Al 2AlN
Emerald Be–Al silicate
H2O
Al Al(OH)3
NaOH or H2O Compounds of Aluminium
Al NaAlO2
Sodium meta
aluminate Aluminium chloride AlCl3 or Al2Cl6
2HCl or Cl2 Preparation of aluminium chloride It is prepared as fol‑
Al AlCl3
H2 SO4 lows:
Al Al2(SO4)3
• By passing dry HCl or Cl2 over heated aluminium.
FA C T TO R E M E M B E R 2Al + 3Cl2 2AlCl3
2Al + 6HCl 2AlCl3 + 3H2
 Al, Fe, Cr, Ni and Co react with concentrated HNO3, HClO4, Dry
H2CrO4 [oxidizing agents], to form a stable oxide layer
over the metal surface. That is why concentrated HNO3 is Macah’s method
Δ
stored in Al-container. Al2O3 + 3C + 3Cl2 2AlCl3 + 3CO ↑
 Al is a very good conductor of electricity Dry

Ag > Cu > Au > Al • When aluminium or aluminium hydroxide is dis‑

 Al–Hg is a reducing agent. solved in dilute HCl, followed by crystallization,
hydrated aluminium chloride is obtained.
2Al + 6HCl 2AlCl3 + 3H2
Uses of Aluminium Dry
• Bronze (Cu + Al), Magnalium (Mg + Al) are used to Al(OH)3 + 3HCl AlCl3 + 3H2O
make aeroplane parts.
Properties of aluminium chloride
• Al is used to make containers for concentrated HNO3
and surgical instruments. • Anhydrous AlCl3 is covalent and acts as a Lewis acid.
• Aluminium foil is used in packing cigarettes. • It is white deliquescent solid and is soluble in organic
• In the reduction of metal oxides (Gold schimidt alu‑ solvents like alcohol and ether.
mino thermite process). • Dimer of AlCl3, that is, Al2Cl6 has both covalent and
• It is used in thermite welding. coordinate bonds.
17.10 Chapter 17

Cl Cl Cl MgSO4 .Al2(SO4)3 .24H2O

FeSO4 .Al2(SO4)3 .24H2O
Al Al
Alums
Cl Cl Cl • In alum crystals, 6 water molecules are held by a
monovalent ion, 6 water molecules are held by
• In AlCl3, Al is sp2 hybridized while in Al2Cl6 Al is sp3 trivalent ion, 12 water molecules are held in the
hybridized. crystal structure.
• During hydrolysis in moist air, AlCl3 gives fumes • All alums are isomorphous.
of HCl and on dissolving in water it changes into • Aqueous solutions of alum are acidic due to cationic
hydrated form. hydrolysis of trivalent cation.
2AlCl3 + 6H2O 2Al(OH)3 + 6HCl • Feature alum or Hair‑salt Al2SO4.18H2O, is a native
Excess form of aluminium sulphate.
2AlCl3 + 12H2O 2[Al(H2O)6]3+.3Cl– • On heating an alum at high temperature it swells up
into a porous mass which is called burnt alum.
• When sodium hydroxide is added slowly and gently
• Alums act as coagulants and have germicide
into AlCl3 solution a white gelatinous precipitate is
properties.
formed which dissolves in excess of sodium hydrox‑
ide to give sodium metaaluminate.
Uses of alums
AlCl3 + 3NaOH Al(OH)3 + 3NaCl
• Alums are used as mordants in dyeing.
Al(OH)3 + NaOH NaAlO2 + 2H2O
• They are used as styptic agents to stop bleeding.
Uses of aluminium chloride • They are used in tanning of leather.
• AlCl3 is used as a catalyst to generate electrophile in • They are used in purification of water (to remove
Friedel Crafts reaction (also in gasoline). negatively charged impurities in water).
• It is used as a mordant in dyeing. Cement
Alums • Cement is used as a building material. It was called
Portland cement by J.Aspdini as on mixing with
• Alums are double salts of M+ and M+3 having a gen‑ water it becomes hard like Portland stone.
eral formula M2I SO4. M2III (SO4)3 .24H2O or MI MIII
• It contains dicalcium silicate (Ca2SiO4, 26%), trical‑
(SO4)2 12H2O
cium silicate (Ca3SiO3, 51%), tricalcium aluminate
Here MI may be K+, Na+, Cs+, NH4+, Rb+, Ag (Li+ is not (Ca3Al2O6, 11.7%), and gypsum (2 to 3%).
possible due to its small size it can not have coordination • Tricalcium aluminate (3CaO.Al2O3) is the fastest set‑
number 6) and MIII may be Fe+3, Cr+3, Mn+3. ting component in cement while dicalcium silicate
• Common alum or potash alum is (2CaO.SiO2) is the slowest setting component.
K2SO4Al2(SO4)3.24H2O
Composition of cement
• If M+3 is Al+3 name of alum is given according to M+.
CaO, SiO2, Al2O3, MgO, Fe2O3, SO3
For example,
62% 23% 7% 2.5% 2.5% 1.5%
Cs2SO4.Cr2(SO4)3.24H2O is called chrome alum.
Manufacture of cement The raw material used for the
• If M+3 is Al+3 name of alum is given according to M+ cement manufacture is lime and clay.
(for example rubidium alum) but not with K+.
• It is manufactured by using these two methods: Wet
• If neither K+ nor Al+3 are present, then name of alum
process and Dry process
is given according to both the cations. For example,
(NH4)2SO4 Fe2 (SO4)3 24H2O is ferric ammonium alum. ∆, strong
Clay + lime Cement clinker
• When in an alum, monovalent element (MI) is substi‑
Gypsum 2% to 3% by weight
tuted by a bivalent element (MII). It is called pseudo Cement
alum. It is not isomorphous with an alum. For example,
CaCO3 CaO + CO2
2CaO + SiO2 2CaO.SiO2
 Chemistry of Lighter Elements 17.11

3CaO + SiO2 3CaO.SiO2 Potassium (K)

3CaO + Al2O3 3CaO.Al2O3
Potassium is a major mineral element and the amount
4CaO + Al2O3 + Fe2O3 4CaO.Al2O3.Fe2O3
required is about 4 g adults and 2–3 g by children per day.
• Gypsum (2% to 3%) is added to cement to slower the
setting process of cement and to make it hard. Function
Setting of Cement • It maintains osmotic pressure, helps in absorption of
water and is essential for conduction of nerve impulse.
• When cement is mixed with water, it forms a gelat‑
inous mass which sets into hard mass due to the • It is an essential component for protein synthesis.
formation of three dimensional cross links between • Potassium acts as a co‑factor for the enzyme pyruvic
[…Si–O–Si…] and […Si–O–Al…] chains. Setting acid kinase.
of cement is an exothermic process. Deficiency Its deficiency causes vomiting, diarrhea, mus‑
Hydration cular weakness, tachycardia and paralysis.
3CaO.Al2O3 + 6H2O 3CaO.Al2O3.6H2O
Colloidal gel
Hydration Calcium (Ca)
2CaO.SiO2 + xH2O 2CaO.SiO2.xH2O
Colloidal gel • Calcium is a major mineral present in the human
Hydration body. It is absorbed from the intestine and its level is
4CaO.Al2O3.Fe2O3 + 6H2O 3CaO.Al2O3
Colloidal gel controlled by vitamin D and parathormone (PTH).
.6H2O + Fe2O3.CaO • Excess by Ca is stored in bones. About 800 mg of
it is required by adults, 1.2 g is needed by pregnant
FA C T TO R E M E M B E R ladies, 350–550 mg by infants per day. 99% calcium
is present in bones and teeth.
 White cement does not have ferric oxide. • In blood, its concentration is regulated by calcitonin
 Fly ash (waste product of steel industry) is added to and parathormones.
cement to reduce its cost.
 Rice husk has high silica content and it is employed to Function
make cement. • It is an essential element for blood clotting and mus‑
cle contraction.
• Calcium controls permeability of cell membranes
BIOLOGICAL ROLE OF Na, K, Mg, Ca and helps in nerve conduction.
Sodium (Na) • It activates enzymes like Atpase, arginine kinase and
succinic dehydrogenase.
• Sodium is a macronutrient and is consumed as NaCl. • Also, it acts as a chemical messenger (IInd messen‑
• The dietary requirement of common salt (NaCl) is ger) in cells.
5–15 g for adults, 1–3 g for childrens and less than
one g for infants per day. Deficiency
• Rickets is caused by the deficiency of calcium in
Functions children and infants.
• Sodium helps in maintaining normal osmotic pres‑ • In adults deficiency of calcium causes osteomala‑
sure between tissue fluids and cells and controls per‑ cia which is a bone disorder. Osteoporosis is caused
meability of cells. especially in women due to Ca deficiency where the
• It takes part in absorption of water, glucose, galac‑ bones become soft due to reduced bone mineral den‑
tose and amino acids. sity leading to easy fractures.
+
• It helps in conduction of nerve impulse and helps to • Low Ca2 level increases blood clotting time.
initiate and regulate heart beat. • Its deficiency also leads to muscular tetany.
• Sodium helps in CO2 transport where it is transferred
as NaHCO3. Magnesium (Mg)
Deficiency Its deficiency leads to sweating, vomiting, • Magnesium is a major mineral required by the human
diarrhea, poor renal functions, muscular pain, low blood body and about 70% of it is found in bones as mag‑
pressure and poor growth of bones. nesium phosphate.
17.12 Chapter 17

• About 200–300 mg of it is required for adults and example, hexokinase, phosphofructokinase, enolase
150–200 mg by children per day. in glycolysis and isocitate dehydrogenase in Krebs
cycle are activated by magnesium.
Function
• It is an important constituent of bones and teeth. Deficiency
• It is essential for binding ribosomal subunits during • Due to the deficiency of magnesium, the sensitivity
protein synthesis and also acts as a co‑factor during of nerves increases and the muscles become weak.
muscle contraction. • Its deficiency causes cardiac arrhythmia and periph‑
• It is an important element for nerve function and eral vasodialation.
activates enzymes of carbohydrate metabolism, for

CONCEPT AT A GLANCE
 Al and BaO2 together act as an ignition mixture.  Sodium sulphate or Glauber’s salt is Na2SO4.10H2O and
 V + Al2O3 is activated alumina. it is used as a purgative and to prepare craft paper, hypo,
 Thermite mixture is [Fe2O3 + Al] + BaO2 soda glass etc.
3 : 1  K+ can be detected in the laboratory by using picric acid
 Na5Al3Si3S3O12 (blue) is termed as ultramarine and is (yellow precipitate formation) or tartaric acid (white
used in calico or blue printing. precipitate).
 Damp Al, S3 emits the foul smell of H2S.  Sodium sesquicarbonate (Na2CO2. NaHCO3.2H2O) is neither
deliquescent nor efflorescent and is used for wool washing.
 An alloy of Na and K is a liquid at room temperature. It is
used in special thermometers for recording temperature  Sodium bicarbonate is present seildlitz powder.
above the boiling point of mercury (357oC).  Polyhalite is K2SO4 .MgSO4 .2CaSO4 .2H2O.
 Chemistry of Lighter Elements 17.13

EXERCISES

Single Option Correct Type

1. Which of the following is an ore of sodium? 10. Sodium amalgam is useful as

(a) chile saltpeter (b) carnalite (a) catalyst
(c) sylvine (d) none of these (b) oxidizing agent
(c) bleaching agent
2. Which of the following is not efflorescent?
(d) reducing agent
(a) CuSO4 (b) NaOH
(c) Na2SO4 (d) MgSO4 11. The oxidation state of sodium in sodium amalgam is
(a) –1 (b) +1
3. Highly pure dilute solution of sodium in liquid ammonia
(c) +2 (d) 0
(a) exhibits electrical neutrality
(b) produces sodium amide 12. In a reaction, sodium is heated with BeCl2. In this
(c) produces hydrogen gas reaction, sodium acts as
(d) show blue colour (a) precipitating agent
(b) hydrolysis agent
4. When carbon monoxide is passed over solid caustic
(c) reducing agent
soda and heated to 200oC, it forms
(d) oxidizing agent
(a) HCOONa (b) Na2CO3
(c) CH3COONa (d) NaHCO3 13. Which of the following does not precipitate in the
Solvay process, for the manufacture of Na2CO3?
5. Which of the following is formed when sodium sul‑
(a) CO2 (b) H2SO4
phate is boiled with powered sulphur?
(c) NH3 (d) NaCl solution
(a) NaHSO4 (b) Na2S2O3
(c) Na2SO4 (d) Na2S4O6 14. Excess of Na+ ions in human system causes
(a) anaemia (b) high blood pressure
6. When sodium bicarbonate is heated, the product
(c) diabetes (d) low blood pressure
obtained is
(a) Na (b) NaCO3 15. Oxone is
(c) NaHCO3 (d) Na2CO3 (a) Na2O2 (b) NaBO3
(c) N2O (d) CaO
7. Carbon decomposes potassium carbonate into
(a) C (b) O 16. When K2O is added to water, the solution is basic
(c) KCN (d) K because it contains a significant concentration of
(a) OH– (b) K+
8. Perchloric acid is prepared by the action of concen‑ 3–
(c) O (d) O22–
trated sulphuric acid on
(a) potassium perchlorate 17. Crystalline sodium chloride is a bad conductor of
(b) barium chlorate electricity because
(c) barium chloride (a) it contains free molecules
(d) sodium chloride (b) the ions present in it are not free to move
(c) it does not possess ions
9. What happens, when a fire caused by potassium in the
(d) it contains only molecules
laboratory is extinguished by pouring water?
(a) there is a decrease in fire intensity 18. Aqueous sodium hydroxide reacts with white phos‑
(b) there is an increase in fire intensity phorous to form phosphine and
(c) the fire completely extinguished (a) P2O3 (b) P2O5
(d) none of these (c) NaH2PO2 (d) Na3PO3
17.14 Chapter 17

19. When sodium is treated with sufficient oxygen/air, the 27. In Solvay process of manufacture of Na2CO3, the by
product obtained is products are
(a) NaO2 (b) NaO (a) CaCl2, CO2, NH3
(c) Na2O (d) Na2O2 (b) Na2CO3, CO2
(c) NH4Cl, CaO
20. In the extraction of sodium by Down’s process, cath‑
(d) CaO, Na2CO3
ode and anode are respectively
(a) nickel and chromium 28. On heating sodium metal in a current of dry ammo‑
(b) iron and graphite nia, the compound formed is
(c) copper and nickel (a) sodium hydride (b) sodium amide
(d) copper and chromium (c) sodium azide (d) sodium nitride
21. In the Castner process of extracting sodium, which of 29. In NaCl, the chloride ions occupy the space in a fash‑
the following reaction occurs at anode ion of
(a) Na+ + e– Na (a) BCC (b) FCC
(b) 4OH– 2H2O + O2 + e– (c) both (d) none
(c) H2 2H+ + 2e–
– 30. When a solution of sodium hydroxide is added in
(d) 2Cl Cl2 + 2e–
excess to the solution of potash alum, we get
22. Sodium is heated in air at 300oC to form X.X absorbs (a) a clear solution
CO2 and forms Na2CO3 and Y. Which of the following (b) a crystalline mass
is Y? (c) a white precipitate
(a) O2 (b) O3 (d) bluish white precipitate
(c) H2 (d) H2O2
31. The pair of compounds which cannot exist together is
23. The product obtained on fusion of BaSO4 and Na2CO3 (a) NaHCO3 and NaOH
is (b) Na2CO3 and NaHCO3
(a) BaO (b) BaCO3 (c) Na2CO3 and NaOH
(c) BaHS4 (d) Ba(OH)2 (d) NaHCO3 and NaCl
24. A mixture of sodium oxide and calcium oxide are 32. Sodium nitrate decomposes above ∼800oC to give
dissolved in water and saturated with excess carbon (a) N2 (b) O2
dioxide gas. The resulting solution is ...…It contains (c) NO2 (d) Na2O
…...
33. Sodium metal reacts with Al2O3 at high temperature
(a) acidic NaOH and CaCO3
to give a sodium compound X.X reacts with carbon
(b) basic Na2CO3 and CaCO3
dioxide in water to form Y.Y is ……
(c) neutral Na2CO3 and CaCO3
(d) basic NaOH and Ca(OH)2 (a) Na2CO3 (b) Na2O2
(c) NaAlO2 (d) Na2O
25. Which one of the following electrolysis is used in
Down’s process of extracting sodium metal? 34. Aqueous solution of NaCl is electrolyzed using plat‑
inum electrodes. What is the product formed at the
(a) NaCl
cathode?
(b) NaCl + NaOH
(c) NaOH + KCl + KF (a) O2 (b) Cl2
(d) NaCl + KCl + KF (c) H2 (d) Na

26. An aqueous solution of sodium carbonate is alkaline 35. Oxalic acid reacts with concentrated H2SO4 to give
because sodium carbonate is a salt of a mixture of two gases. When this mixture is passed
through caustic potash, one of the gases is absorbed.
(a) weak acid and weak base
What is the product formed by the absorbed gas with
(b) weak acid and strong base
caustic potash?
(c) strong acid and strong base
(d) strong acid and weak base (a) KHCO3 (b) K2CO3
(c) KOH (d) K2SO4
 Chemistry of Lighter Elements 17.15

36. In organic reactions, sodium in liquid ammonia is 46. Mortar is a mixture of

used as …… (a) slaked lime + silica + H2O
(a) oxidizing agent (b) CaCO3 + silica + H2O
(b) reducing agent (c) slaked lime + plaster of paris +H2O
(c) hydrolyzing agent (d) plaster of paris + silica
(d) precipitating agent
47. Which of the following is an alloy of aluminium?
37. Which one of the following compounds in aqueous (a) magnallium (b) duralumin
solution gives a white precipitate with perchloric acid? (c) brass (d) both (a) and (b)
(a) NaCl (b) MgCl2
48. What is the molecular formula of gypsum?
(c) KCl (d) FeCl3
(a) CaSO4.2H2O (b) CaSO4.3H2O
38. Which of the following ore contains both calcium and (c) CaSO4.H2O (d) 2CaSO4.H2O
magnesium?
49. In the Castner’s process of extraction of sodium
(a) lime stone (b) dolomite
cathode is
(c) epsom salt (d) carnalite
(a) nickel rod (b) iron rod
39. Magnesium does not decompose in (c) graphite rod (d) copper rod
(a) hot water (b) steam
50. Which of the following is incorrect?
(c) semi hot water (d) cold water
(a) Mg burns in air releasing dazzling light rich in
40. Which of the following is the composition of carnalite? uv rays
(a) MgCl2.KCl.6H2O (b) CaCl2.6H2O when mixed with ice gives a freezing
(b) Fe3O4 mixture
(c) Na3AlF6 (c) Mg cannot form complexes
(d) Na2Al2O3 (d) Be can form complexes due to its very small size
41. Which of the following is produced when magnesium 51. An important ore of magnesium is
reacts with hot concentrated H2SO4? (a) malachite (b) cassiterite
(a) H2 (b) S (c) carnalite (d) galena
(c) MgO (d) SO2
52. Mg is an important component of which biomolecule
42. MgCl2.6H2O, when heated gives occurring extensively in living world?
(a) magnesium hydride (a) cholorophyll (b) haemoglobin
(b) magnesium chloride (c) ATP (d) florigen
(c) magnesium oxide
53. Plaster of paris is used
(d) magnesium oxychloride
(a) in dentistry and surgery
43. Aqueous solution of carnalite gives a positive test (b) as a plaster for walls
for (c) as a drying agent
(a) potassium, magnesium and chloride ions (d) in metallurgical process
(b) potassium ions only
54. The reaction of slaked lime with Cl2 gas gives
(c) potassium and chloride ions only
(d) chloride ions only (a) a mixture of Ca(OCl)2, Ca(OH)2, CaCl2 and H2O
(b) quick lime
44. Which of the following is calcium superphosphate? (c) Baryta water
(a) Ca(H2PO4)2H2O + CaSO4 (d) only Ca(OCl)2
(b) CaSO4 + CaO
55. The compound insoluble in acetic acid is
(c) Ca3(PO4)2 + 2CaSO4
(d) Ca(H2PO4)2H2O + 2(CaSO2.2H2O) (a) calcium oxide
(b) calcium carbonate
45. What is the molecular formula of plaster of paris? (c) calcium oxalate
(a) CaSO4.2H2O (b) 2CaSO4.H2O (d) calcium hydroxide
(c) 2CaSO4.2H2O (d) CaSO4.3H2O
17.16 Chapter 17

56. The hydration energy or Mg2+ ions is higher than that (c) dehydration and dehydrolysis
of (d) hydration and gel formation
(a) Al3+ (b) Be2+ 67. What are the products formed when an aqueous solu‑
+
(c) Na (d) none of these tion of magnesium bicarbonate is boiled?
57. On heating quick lime with coke in an electric fur‑ (a) Mg, CO2, H2O
nace, we get (b) Mg(OH)2, H2O
(a) CaC2 (b) CaCO3 (c) MgCO3, H2O, CO2
(c) CaO (d) Ca and CO2 (d) Mg(HCO3)2, H2O
58. Limestone is not used in which of the following man‑ 68. Silica reacts with Mg to form a magnesium com‑
ufacturing processes? pound X. X reacts with dilute HCl and forms Y. Y is
(a) Portland cement (a) MgCl2 (b) MgO
(b) phosphorus from phosphorite (c) SiCl4 (d) MgSiO
(c) iron form haematite 69. One of the elements present in carnalite shows flame
(d) Solvay process of sodium carbonate colouration. The colour of the flame is
59. Solution of MgCl2 in water has pH value (a) green (b) lilac
(a) 7 (b) > 7 (c) yellow (d) orange
(c) < 7 (d) 14.2 70. In which of the following reactions MgO is not
60. A solution of Ca in liquid ammonia when evaporated formed?
to dryness gives as residue of (a) Mg + B2O3
(a) [Ca(NH3)x]2+ (b) Ca(NH3)6 (b) Mg + NO2
(c) pure Ca (d) [Ca(NH3)6]2+ (c) Mg + dil.HNO3
(d) Mg + CO2
61. Magnesium can be obtained by
(a) reducing magnesium salt solution with Fe 71. Which one of the following is dead burnt plaster?
(b) electrolysis of fused magnesium salt (a) anhydrous CaSO4
(c) electrolysis of Mg(NO3)2 solution (b) CaSO3
(d) reducing MgO with coke (c) (CaSO4)2.H2O
(d) CaSO4.2H2O
62. The compound formed when gypsum is dissolved in
aqueous ammonium sulphate solution is 72. Aluminium vessles should not be washed with mate‑
(a) CaSO4.NH3Cl.H2O rials containing washing soda because
(b) CaSO4.(NH4)2SO4.H2O (a) washing soda reacts with aluminum to form
(c) CaCl2.NH4Cl.2H2O insoluble aluminium oxide
(d) CaCl2.(NH4)2SO4.H2O (b) washing soda reacts with aluminium to form sol‑
uble aluminate.
63. Fluorosis disease is caused due to the reaction of (c) washing soda is expensive
…….with excess of fluoride in the body. (d) washing soda is easily decomposed
(a) Mg (b) Fe
(c) K (d) Ca 73. Aluminium reacts with concentrated HNO3 and
(a) liberates O2 (b) liberates N2
64. Which of the following is insoluble in water? (c) becomes passive (d) forms AIN
(a) CaF2 (b) NaCl
(c) HgCl2 (d) Ca(NO3)2 74. Which of the following is obtained when NH4OH is
added to AlCl3 solution?
65. Carnalite on electrolysis gives (a) NH3 (b) NH4Cl
(a) Na and CO2 (b) Mg and Cl2 (c) NH4 (d) Al(OH)3
(c) Al and Cl2 (d) Ca and Cl2
75. Which of the following is formed when aluminium
66. Initial setting of cement is mainly due to nitride is heated with HCl at 900oC?
(a) hydration and hydrolysis (a) AlCl3 (b) AlH3
(b) dehydration and gel formation (c) Al2Cl3 (d) NH4Cl
 Chemistry of Lighter Elements 17.17

76. The composition of diaspore is placed a pellet of NaOH on a watch glass. A few days
(a) Al2O3.3H2O (b) Al2O3.H2O later, he noticed that the pellet was covered with a
(c) Al2O3 (d) Al2O3.2H2O white solid. Identify this white solid?
(a) Na metal (b) Na2SO3
77. The reducing agent in thermite process is
(c) Na2CO3 (d) Na2S
(a) Mg (b) BaO2
(c) Al (d) MnO2 88. In the reaction: K4 [Fe(CN)6] + K2CO3 the
product formed is
78. What is formed when aluminium trioxide reacts with
(a) FeCO3 (b) KCN
sodium?
(c) KFeCO3 (d) K3 [Fe(CN)4]
(a) NaO (b) NaO2
(c) Na2O (d) Na2O2 89. Which one of the following reactions is not associated
with the Solvay process of manufacture of sodium
79. The alum used for purifying water is carbonate?
(a) potash alum (b) chrome alum (a) NaCl + NH4CO3 NaHCO3 + NH4Cl
(c) ferric alum (d) ammonium alum (b) 2NaOH + CO2 Na2CO3 + H2O
80. What is formed when nitrogen reacts with alumina in (c) 2NaHCO3 Na2CO3 + H2O + CO2
presence of carbon at 2100K? (d) NH3 + H2CO3 NH4HCO3
(a) AlN2 (b) AlN 90. In electrolysis of NaCl when Pt electrode is used, then
(c) AlN3 (d) AlC2 H2 is liberated at cathode while with Hg cathode it
81. Which of the following alloy is used for making forms sodium amalgam. The reason for this is
magnets for hearing aids? (a) more voltage is required to reduce H+ at Hg than
(a) invar (b) german silver at Pt
(c) monel metal (d) alnico (b) concentration of H+ ions is larger when Pt elec‑
trode is taken.
82. Emery consists of impure (c) Na is dissolved in Hg while it does not dissolve
(a) iron (b) corundum in Pt
(c) carborundum (d) graphite (d) Hg is more inert than Pt
83. The molecular formula of potash alum is 91. A certain metal M is used to prepare an antacid, which
(a) K2Al2S2H48O39 (b) KAl2S2H48O40 is used as a medicine for acidity. This metal accidently
(c) K2AlS2H48O40 (d) K2Al2S2H48O40 catches fire, which can not be extinguished by using
CO2 based extinguishers. The metal M is
84. Which of the following is not correct?
(a) Mg (b) Ba
(a) Al reacts with NaOH and liberates H2 (c) Be (d) C
(b) AlCl3 is a Lewis acid
(c) Al is used in the manufacture of electrical cables 92. In the detection of sulphur, sodium nitroprusside
(d) NaOH is used during Halls process of purifica‑ solution is added to the Lassaigne’s test solution, a
tion of bauxite purple coloured is obtained. It is due to
(a) Na3 [Fe(CN)5 NOSNa]
85. Which of the following is known as pseudo alum?
(b) Na3 [Fe(CN)6]
(a) K2SO4. Al2(SO4)3.24H2O (c) Fe(CNS)3
(b) KCr(SO4)2.12H2O (d) Na3 [Fe(CN)5NS]
(c) KMn(SO4)2.12H2O
(d) NH4 Fe(SO4)2.12H2O 93. In the reaction:
Al2(SO4)3.18H2O Heat 800OC B + C.
A
86. Which of the following compound transforms baking –18 H2O
soda into baking powder? The product A, B and C are respetively
(a) KHCO3 (b) NaHCO3 (a) Al2(SO4)3, Al2O3, SO3
(c) KHC4H4O6 (d) KCl (b) Al2O3, Al2(SO4)3, SO3
(c) Al2SO4, Al2O3, SO3
87. Sodium hydroxide being hygroscopic absorbs mois‑
(d) Al2(SO4)3, Al2O3, SO2
ture when exposed to the atmosphere. A student
17.18 Chapter 17

94. Gas ‘A’ is bubbled through slaked lime when a white Y can be converted to X on heating with …….
precipitate is formed. On prolonged bubbling the pre‑ at……….temperature.
cipitate dissolved. On heating the resultant solution, (a) Cu, 300oC
the white precipitate reappeared with solution of gas (b) Al2O3, 350oC
‘B’. The gases ‘A’ and ‘B’ respectively are (c) NaOH/I2, 60oC
(a) CO and CO2 (b) CO2 and CO2 (d) Ca(OH)2 + CaOCl2, 60oC
(c) CO and CO (d) CO2 and CO 101. A metal (A) heating in nitrogen gas gives (B). (B) on
95. Which of the following set of raw materials are used treatment with H2O gives a colourless gas which on
in the manufacture of Na2CO3 by Solvay process? passing through CuSO4 solution turns it deep blue.
(a) CaCl2, NH3, CO2 Here (B) is
(b) NaOH, NH3, CO2 (a) NH3 (b) MgO
(c) NaCl, NH3, CO2 (c) Mg(NO3)2 (d) Mg3N2
(d) Ca(OH)2, NH3, CO2 102. When washing soda is heated
(a) CO2 is released
96. A burning strip of magnesium is introduced into a (b) water vapour is released
jar containing a gas. After sometimes the walls of the (c) CO2 is released
container is coated with carbon. The gas in the con‑ (d) CO + CO2 is released
tainer is
(a) H2O (b) CO2 103. Which of the following is correct?
(c) O2 (d) N2 (a) sodium reduces CO2 to carbon
(b) in the Castner’s process of sodium extraction,
97. Halides of alkaline earth metals form hydrates
NaCl is used as an electrolyte
such as MgCl2.6H2O, CaCl2.6H2O, BaCl2.2H2O
(c) magnalium is an alloy of Mg and Zn
and SrCl2.2H2O. This shows that halides of group
(d) Mg reacts with cold water and liberate hydrogen
2 elements
gas
(a) can absorb moisture form air
(b) act as dehydrating agents 104. MgSO4 on reaction with NH4OH and Na2HPO4 forms
(c) are hydroscopic in nature a white crystalline precipitate. What is its formula?
(d) all of the above (a) Mg(NH4)PO4 (b) Mg3(PO4)2
(c) MgCl2.MgSO4 (d) MgSO4
98. A deliquescent white crystalline hydroxide X reacts
with a nitrate Y to form another hydroxide which 105. A sodium salt on treatment with MgCl2 gives white pre‑
decomposes to give a insoluble brown layer of its cipitate only on heating. The anion of the sodium salt is
oxide. X is a powerful cautery and breaks down then (a) HCO3– (b) CO32–
proteins of skin flesh to a pasty mass. X and Y are (c) NO3 –
(d) SO42–
(a) NaOH, Zn(NO3)2
106. The metallic lusture exhibited by sodium is explained
(b) NaOH, AgNO3
by
(c) Ca(OH)2.HgNO3
(d) NaOH, Al(NO3)3 (a) diffusion of sodium ions
(b) oscillation of loose electrons
99. Solution of sodium metal in liquid ammonia is strongly (c) excitation of free electrons
reducing due to the presence in solution of the following (d) existence of body centred cubic lattice.
(a) solvated electrons
107. Which of the following changes occur when an excess
(b) sodium atoms
of CO2 gas is passed into a clear solution of lime water?
(c) sodium hydride
(d) sodium amide (a) a white precipitate containing both CaCO3 and
Ca(HCO3)2 is formed
100. Consider the following reactions: (b) initially a white precipitate of CaCO3 is formed
Anhyd. AlCl3 which changes into soluble Ca(HCO3)2 on pass‑
X + HCl C2H5Cl
(addition) ing CO2 gas
Anhyd. ZnCl2/HCl3
(c) a white precipitate of Ca(HCO3)2 is formed
(substitution) (d) a white precipitate of CaCO3 is formed
 Chemistry of Lighter Elements 17.19

108. Sodium sulphate is soluble in water whereas barium 114. Aluminium is more reactive than iron because its
sulphate is sparingly soluble because standard reduction potential is higher. Still aluminium
(a) the hydration energy of sodium sulphate is more is less easily corrdoed than iron because
than its lattice energy (a) Al reacts with atmospheric carbon dioxide to
(b) the lattice energy of barium sulphate is less than form a self protective layer of Al2O3
its hydration energy (b) it has higher reducing power and forms a self pro‑
(c) the lattice energy has no role to play in solubility tective layer of Al2O3
(d) the hydration energy of sodium sulphate is less (c) it has higher reducing power and does not react
than its lattice energy with oxygen so easily
(d) both (a) and (b)
109. If NaOH is added to an aqueous solution of Zn2+ ions,
a white precipitate appears and on adding excess 115. Some large white transparent crystals are left out in a
NaOH, the precipitate dissolves. In this solution zinc bowl for several days. They are then observed to have
exists in the changed their form into white powder. The crystals
(a) anionic part may have been of
(b) cationic part (a) calcium oxide
(c) both in anionic and cationic parts (b) sodium carbonate
(d) there is no zinc left in the solution (c) ammonium chloride
(d) sodium chloride
110. When sodium chloride is electrolyzed in Nelson’s
cell, hydrogen is liberated at cathode and not sodium, 116. The dissolution of Al(OH)3 by a solution of NaOH
because results in the formation of
(a) H+ does not react with water (a) [Al (H2O)6 (OH)3] (b) [Al (H2O)4 (OH)]2+
(b) H+ has lower electrode potential (c) [Al (H2O)2 (OH)4] –
(d) [Al (H2O)3 (OH)3]
(c) H+ has greater mobility than Na+
117. A solution when diluted with water and boiled, gives
(d) H+ is smaller than Na+
a white precipitate. On addition of excess of NH4Cl/
111. 2 g of aluminium is treated separately with excess of NH4OH, the volume of precipitate decreases, leaving
dilute H2SO4 and excess of NaOH. The ratio of the behind a white gelatinous precipitate. Identify the
volumes of hydrogen evolved is precipitate which dissolves in NH4OH/NH4Cl.
(a) 1:1 (b) 1 : 2 (a) Al(OH)3 (b) Ca(OH)2
(c) 2 : 1 (d) 2 : 3 (c) Mg(OH)2 (d) Zn(OH)2
112. Which of the following reactions written here are
118. In the following sequence of reactions, identify the
correct?
end product (D).
(1) B + NaOH 2Na3BO3 + H2 SO2 Na2CO3
(2) P4 + NaOH + H2O NaH2PO2 + PH3 Na2CO3 (A) (B)
Δ I2
(3) S + NaOH Na2S2O3 + Na2S + H2O Elemental S (C) (D)
(a) 1 only (b) 3 only (a) Na2SO4 (b) Na2S4O6
(c) 2 and 3 (d) 1, 2 and 3 (c) Na2S (d) Na2S2O3
113. Match the following: 119. 1.04 g of bleaching powder was made into a paste
List I List II with water and then the volume was made upto 200
1. Sorel’s cement (i) MgCl2 ml. 25 ml of this solution was found to oxidize 13.4
2. Albite (ii) MgO ml of a standard solution of arsenic containing 4.3 g
3. A salt of carnalite (iii) NaAlSi3O8 Al2O3 per litre. Find the percentage available chlorine
4. Glauber’s salt (iv) Na2SO4.10H2O in the sample.
The correct matching is: (a) 31.7% (b) 36.7%
1 2 3 4 (c) 41.7% (d) 63.6%
(a) (ii) (iii) (iv) (i)
(b) (iv) (ii) (ii) (i) 120. A white, water‑insoluble solid (A), is attacked by an
(c) (iii) (ii) (i) (iv) acid, liberating a colourless, odourless gas (B), leav‑
(d) (ii) (iii) (i) (iv) ing a clear solution (C). The solution (C) gives a white
precipitate (D) on addition of dilute H2SO4, (C) gives
17.20 Chapter 17

a yellow precipitate (E) on addition of K2CrO4 solu‑ 126. Consider the following reactions:
tion. Gas (B) bubbled through a suspension of CaCO3 1. 2Na + 2H2O 2NaOH + H2
causesdis solution of that compound. Identify (E). 2. 2NaOH + Cl2 NaCl + NaOCl + H2O
(a) CaCrO4 (b) BaCr2O7 3. 4OH– O2 + 2H2O + 4e–
(c) BaCrO4 (d) none of these 4. 2Cl– Cl2 + 2e–
In the diaphragm cell used for the electrolysis of
121. The aqueous solution of an inorganic compound (X),
brine, the reactions that occur would include
gives a white precipitate with NH4OH, which does not
(a) 2, 3, 4 (b) 1, 3, 4
dissolve in excess of NH4OH. This aqueous solution
(c) 1, 2, 3 (d) 1, 2, 4
also gives white precipitate with AgNO3 and the pre‑
cipitate is soluble in dilute HNO3. Here (X) is 127. When brine solution is saturated with NH3 and CO2
(a) AlCl3 (b) AlBr3 a slightly alkaline white sodium salt (A) is formed
(c) AlN (d) Al2(SO4)3 which has pH of nearly 8.4. (A) on heating liberates
a gas (B) leaving a highly alkaline residue (C) of pH
122. Match the following: nearly 10 to 11. Gas (B) is colourless and turns a solu‑
List I List II tion of Ca(OH)2 milky. Identify (B).
1. efflorescent (i) NaOH (a) Na2CO3 (b) NaHCO3
2. deliquescent (ii) KOH (c) Na2S (d) Na2SO4
3. fusion mixture (iii) Na2CO3 and K2CO3
4. washing soda (iv) Na2CO3.10H2O 128. Consider the following statements:
The correct matching is 1. Cs+ ion is more highly hydrated than other alkali
1 2 3 4 metal ions
(a) (ii) (i) (iv) (iii) 2. Among the alkali metals Li, Na, K and Rb, Li has
(b) (i) (ii) (iii) (iv) the higher melting point
(c) (ii) (i) (iii) (iv) 3. Among the alkali metals, only Li form a stable
(d) (i) (iii) (iv) (ii) nitride by direct combination
(a) 1 and 3 are correct
123. The major role of fluorspar (CaF2) which is added in
(b) 2 and 3 are correct
small quantities in the electrolytic reduction of alu‑
(c) 1, 2 and 3 are correct
mina dissolved in fused cryolite (Na3AlF6) is
(d) 1 and 2 are correct
1. as a catalyst
2. to make the fused mixture very conducting 129. Metal X on heating in nitrogen gas gives Y.Y on
3. to lower the temperature of melt treatment with H2O gives a colourless gas which
4. to decrease the rate of oxidation of carbon at the when passed through CuSO4 solution gives a blue
anode colour. Y is
(a) 2, 3 (b) 1, 2 (a) MgO (b) Mg(NO3)2
(c) 2, 3, 4 (d) 3, 4 (c) Mg3N2 (d) NH3
124. In the following sequence of reactions. Identify (E)? 130. Highly pure dilute solution of sodium in liquid
Δ, ZnCl2 ammonia
Na2CO3 + H2O + CO2 (A)
Δ NaOH 1. shows blue colour
(B) (C) + (D) ↑ (E)
2. exhibits electrical conductivity
(a) NaHCO3 (b) Na2O2 3. produces sodium amide
(c) Na2ZnO2 (d) ZnCO3 4. produces hydrogen gas
125. The pair of compounds which cannot exist together in (a) 1, 2 (b) 1, 2, 3
aqueous solution is (c) 2, 3, 4 (d) all of these
1. NaH2PO4 and Na2HCO3
2. Na2CO3 and NaHCO3 131. Out of the following metals, those that cannot be
3. NaOH and NaH2PO4 obtained by electrolysis of the aqueous solution of
4. NaHCO3 and NaOH their salts are
(a) 1, 2, 3 (b) 3, 4 1. Ag 2. Mg
(c) 1, 4 (d) 2, 3 3. Cu 4. Al
 Chemistry of Lighter Elements 17.21

(a) 2, 4 (b) 2, 3 133. Match the following:

(c) 1, 4 (d) all List–I List–II
1. Beryl (i) KCl.MgCl2.6H2O
132. When zeolite, which is hydrated sodium aluminium
silicate, is treated with hard water the sodium ions are 2. Carnalite (ii) MgCO3
exchanged with 3. Asbestos (iii) 3BeO.Al2O3.6SiO2
4. Magnesite (iv) Ca2 Mg5 Si8 O22 (OH)2
1. H+ ions 2. Ca2+ ions
(v) CaSO4.2H2O
3. SO4–2 ions 4. Mg2+ ions
The correct matching is:
(a) 2, 4 (b) 1, 2, 3 1 2 3 4
(c) 2, 4, 5 (d) all are correct
(a) (iii) (iv) (i) (ii)
(b) (iv) (iii) (ii) (i)
(c) (iii) (i) (iv) (ii)
(d) (iii) (i) (ii) (iv)

More than One Option Correct Type

134. Select the correct statement(s): 138. Select the correct statement(s):
(a) BaSO4 is soluble in water (a) Be dissolves in alkali forming [Be(OH)4]2–
(b) Ba(OH)2 is soluble in water (b) BeF2 forms complex ion with NaF in which Be
(c) MgSO4 is soluble in water goes with cation
(d) CaF2 is soluble in water (c) BeCO3 is kept in the atmosphere of CO2 since, it
is least thermally stable
135. Select the incorrect statement(s):
(d) BeF2 forms complex ion with NaF in which Be
(a) Milk of magnesia is an aqueous solution of goes with anion.
Mg(OH)2
(b) KOH is a weaker base than NaOH 139 The pair of compounds which cannot exist together in
(c) CaO2 is less stable than MgO2 aqueous solution is [IIT 1992]
(a) NaH2PO4 and Na2HCO3
(d) Mg2+ ions are precipitated with the addition of
(b) Na2CO3 and NaHCO3
NH4OH in the presence of NH4Cl
(c) NaOH and NaH2PO4
136. Select the correct statement(s) are: (d) NaHCO3 and NaOH
(a) Na2CO3.NaHCO3.2H2O is a mineral called trona.
140. Nitrate of which of the following elements can be
(b) Li2CO3 and MgCO3 both are thermally stable converted into their oxides on heating?
(c) Li2CO3 is only sparingly soluble in water and no (a) Na (b) Li
LiHCO3 has been isolated. (c) Mg (d) Rb
(d) K2CO3 cannot be made by a method similar to the
141. Which of the following carbonates cannot evolve CO2
ammonia‑soda process. on heating?
137. Which of the following statement(s) is/are true? (a) Na2CO3 (b) Rb2CO3
(a) Stability of alkali metal peroxide increases with (c) Li2CO3 (d) MgCO3
increase in atomic number 142. Sodium sulphate is soluble in water whereas barium
(b) Hydration energy of AgF is higher than its lattice
sulphate is sparingly soluble because [IIT 1988]
energy
(c) Anhydrous MgCl2 cannot be prepared by direct (a) The hydration energy of sodium sulphate is more
heating of MgCl2.6H2O than its lattice energy
(d) The milk of magnesia used as antacid is chemi‑ (b) The lattice energy of barium sulphate is more
than its hydration energy
cally MgO + MgCl2
17.22 Chapter 17

(c) The lattice energy has no role to play in solubility (c) The hybridisation state of Be in BeCl2 is sp3
(d) The hydration energy of sodium sulphate is less (d) BeCl2 can form dimer
than its lattice energy.
146. Gypsum on heating gives:
143. Which of the following oxides have rock salt structure (a) CaS + O2 (b) CaO + SO3
with coordination number 6 : 6. (c) CaSO4. ½ H2O (d) CaSO4
(a) MgO (b) CaO
147. Which of the following metals are extracted by using
(c) SrO (d) B2O3
Al as a reducing agent?
144. Mg and Zn have following resemblance: (a) W from WO3 (b) Mg from MgO
(a) Both of them can be used as electrodes (c) Na from Na2O (d) Cr from Cr2O3
(b) MgO and ZnO are amphoteric.
(c) Both of them can be used to prevent corrosion 148. Which is true about beryllium?
(d) MgCO3, ZnCO3 both on heating give their oxides. (a) Be(OH)2 is basic in nature only.
(b) Beryllium halides are electron deficient.
145. Out of the following the correct statement is/are: (c) Aqueous solution of BeCl2 is acidic.
(a) BeCl2 is an electron deficient molecule (d) It forms unusual carbide Be2C.
(b) BeCl2 is a covalent compound

Passage Based Questions

Passage-1 (c) (D) = NH4HCO3, (E) = Na2CO3,
(F) = NaHCO3
Consider the reactions given below and answer the
questions: (d) None of these
(A) Δ (B) (oxide) + CO2 Passage-2
(B) + H2O → (C)
Element A burns in nitrogen to give an ionic com‑
(C) + CO2 → (A) (milky)
Δ
pound B. Compound B reacts with water to give C
(D) + NH4Cl (D) gas and D. A solution of C becomes ‘milky’ on bubbling
(E) + H2O + CO2 → (E) carbon dioxide.
(F) + NaCl → (F)
Δ 152. Here the element (A) is
(G) Na2CO3 + CO2 + H2O
(a) Mg (b) Na
149. Here compound (A) is: (c) Ca (d) K
(a) CaO
(b) Na2CO3 153. Her compound (B) and (C) are respectively:
(c) CaCO3 (a) Calcium carbide and acetylene
(d) Ca(HCO3)2 (b) Calcium nitride and calcium hydroxide
(c) Magnesium nitride and magnesium hydroxide
150. Here compound (B) and (C) are respectively:
(d) Magnesium carbide and propyne
(a) Ca(OH)2 and CaCO3
(b) CaO and Ca(OH)2 154. Which is incorrect about this element?
(c) Ca(OH)2, CaO (a) It forms basic oxide and basic hydroxide
(d) CaCO3 and Ca(OH)2 (b) Its carbonate decomposes on heating
(c) It can form stable complexes even with weak
151. Here (D), (E) and (F) are respectively: complexing agents also
(a) (D) = NH3, (E) = NH4HCO3, (d) It is essential constituent of bones and teeth.
(F) = NaHCO3
(b) (D) = NH3, (E) = NH4Cl,
(F) = NH4HCO3
 Chemistry of Lighter Elements 17.23

Passage-3 155. Here (X) is

(a) KHCO3 (b) Na2CO3
When 16.8 g of white solid X were heated, 4.4 g of
acid gas A that turned lime water milky was driven (c) NH4HCO3 (d) NaHCO3
off together with 1.8 g of a gas B which condensed 156. Here (A) and (B) are respectively:
to a colourless liquid. The solid that remained, Y, dis‑ (a) CO2 and N2 (b) CO2 and H2
solved in water to give an alkaline solution, which
(c) CO2 and H2O (d) CO2 and NH3
with excess barium chloride solution gave a white
precipitate Z. The precipitate effervesced with acid 157. Here (Y) and (Z) are respectively:
giving off carbon dioxide. (a) NaHCO3 and BaHCO3
(b) Na2CO3 and BaCO3
Identify A, B and Y and write down the equation for
(c) NaOH and BaCO3
the thermal decomposition of X. (d) K2CO3 and BaCO3

Match the Column Type

p q r s 160. Match the following

(a) O O O O
Column–I Column–II
(b) O O O O
(c) O O O O (a) Castner Kellner (p) MgCl2.5MgO.xH2O
(d) O O O O cell
(b) Pearl ash (q) K2CO3
158. Match the following
(c) Solvay’s process (r) Manufacture of NaHCO3
Column–I Column–II
(d) Sorel’s cement (s) Manufacture of NaOH
(a) Na2CO3 (p) SO2 absorber
(b) Na2SO3 (q) Detergent 161. Match the following
(c) NaOH (r) Glass Column–I Column–II
(d) NaOCl (s) Bleach
(a) Magnesia (p) MgSO4.7H2O
159. Match the following (b) Epsom salt (q) MgO
List–I (Compounds) List–II (Use of (c) Anhydrone (r) CaH2
compounds) (d) Hydrolith (s) Mg(ClO4)2
(a) Magnesium hydroxide (p) As a fertilizer
162. Match the following
(b) Barium sulphate (q) As a purgative
(c) Magnesium sulphate (r) As a constituent of List–I List–II
lithopone
(a) Aqueous solution of (p) Anhydrone
(d) Calcium cyanamide (s) As a constituent of NaOCl
sorrel cement (b) KClO3 (q) Javelle water
(c) Mg(ClO4)2 (r) Euchlorine
(d) Cl2 and ClO2 mixture (s) Berthelot’s salt
17.24 Chapter 17

Previous Years' Questions

163. KO2 (potassium super oxide) is used in oxygen cylin‑ 168. Several blocks of magnesium are fixed to the bottom
ders in space and submarines because it [2002] of a ship to [2003]
(a) produces ozone (a) keep away the sharks
(b) absorbs CO2 (b) prevent action of water and salt
(c) absorbs CO2 and increase O2 contents (c) make the ship lighter
(d) eliminates moisture (d) prevent puncturing by under sea rocks
164. A metal M readily forms water soluble sulphate 169. Beryllium and aluminium exhibit many properties
MSO4, water insoluble hydroxide M(OH)2 and oxide which are similar. But the two elements differ in
MO which becomes inert on heating. The hydroxide [2004]
is soluble in NaOH. M is [2002] (a) forming polymeric hydrides
(a) Mg (b) Sr (b) forming covalent halides
(c) Be (d) Ca (c) exhibiting maximum covalency in compounds
165. Metallic sodium dissolves in liquid ammonia to form (d) exhibiting amphoteric nature in their oxides.
a deep blue coloured solution. The deep blue colour is 170. Heating an aqueous solution of aluminium chloride to
due to formation of [2002] dryness will give [2005]
–
(a) solvated electron, e (NH3)x y (a) AlCl3 (b) Al2Cl3
(b) solvated atomic sodium, Na(NH3)y (c) Al(OH)Cl2 (d) Al2Cl6
(c) [Na+ + Na–]
171. Which of the following on thermal – decomposition
(d) NaNH2 + H2
yields a basic as well as an acidic oxide? [2012]
166. In curing cement plasters, water is sprinkled from (a) CaCO3 (b) NaNO3
time to time. This helps in [2003] (c) KClO3 (d) NH4NO3
(a) hydrating sand gravel mixed with cement
(b) keeping it cool 171. The mainoxides formed on combusting of Li, Na and
(c) converting sand into silicic acid K in excess of air are respectively? [2016]
(d) developing interlocking needle like crystals of (a) LiO2, Na2O2 and K2O
hydrated silicates (b) Li2O2, Na2O2 and KO2
(c) Li2O, Na2O2 and KO2
167. The substance not likely to contain CaCO3 is [2003] (d) Li2O, Na2O and KO2
(a) sea shells (b) calcined gypsum
(c) dolomite (d) a marble statue

ANSWER KEYS

Single Option Correct Type

1. (a) 2. (b) 3. (d) 4. (a) 5. (b) 6. (d) 7. (d) 8. (a) 9. (b) 10. (d)
11. (d) 12. (c) 13. (b) 14. (b) 15. (a) 16. (a) 17. (b) 18. (c) 19. (d) 20. (b)
21. (b) 22. (a) 23. (b) 24. (b) 25. (d) 26. (b) 27. (a) 28. (b) 29. (b) 30. (a)
31. (a) 32. (b) 33. (a) 34. (c) 35. (b) 36. (b) 37. (c) 38. (b) 39. (d) 40. (a)
41. (d) 42. (b) 43. (a) 44. (d) 45. (b) 46. (a) 47. (d) 48. (a) 49. (b) 50. (c)
51. (c) 52. (a) 53. (b) 54. (a) 55. (c) 56. (c) 57. (a) 58. (b) 59. (c) 60. (b)
61. (b) 62. (b) 63. (d) 64. (a) 65. (b) 66. (d) 67. (c) 68. (a) 69. (b) 70. (c)
71. (a) 72. (b) 73. (c) 74. (d) 75. (a) 76. (b) 77. (c) 78. (c) 79. (a) 80. (b)
81. (d) 82. (b) 83. (d) 84. (d) 85. (a) 86. (c) 87. (c) 88. (b) 89. (b) 90. (d)
 Chemistry of Lighter Elements 17.25

91. (a) 92. (a) 93. (a) 94. (b) 95. (c) 96. (b) 97. (d) 98. (b) 99. (a) 100. (b)
101. (d) 102. (b) 103. (a) 104. (a) 105. (a) 106. (b) 107. (b) 108. (a) 109. (a) 110. (c)
111. (a) 112. (d) 113. (d) 114. (b) 115. (b) 116. (c) 117. (a) 118. (b) 119. (a) 120. (c)
121. (a) 122. (c) 123. (a) 124. (c) 125. (b) 126. (b) 127. (a) 128. (b) 129. (c) 130. (a)
131. (a) 132. (a) 133. (c)

More than One Option Correct Type

134. (b, c) 135. (b, d) 136. (a, c, d) 137. (a, b, c) 138. (a, c, d) 139. (c, d) 140. (b, c)
141. (a, b) 142. (a, b) 143. (a, b, c) 144. (a, c, d) 145. (a, b, d) 146. (b, c, d) 147. (a, d)
148. (b, c, d)

Passage Based Questions

149. (c) 150. (b) 151. (a) 152. (c) 153. (b) 154. (c) 155. (d) 156. (c) 157. (b)

Match the Column Type

158. a → (q); b → (r); c → (p); d → (s) 159. a → (s); b → (r); c → (q); d → (p)
160. a → (s); b → (q); c → (r); d → (p) 161. a → (q); b → (p); c → (s); d → (r)
162. a → (q), b → (s); c → (p); d → (r)

Previous Years' Questions

163. (c) 164. (c) 165. (a) 166. (d) 167. (b) 168. (c) 169. (a) 170. (d) 171. (a) 172. (c)
17.26 Chapter 17

HINTS AND SOLUTIONS

Single Option Correct Type

2. NaOH is not efflorescent, as its crystals do not loose water. 55. Calcium oxalate does not dissolve in acetic acid. All others
3. The blue colour is due to formation of ammoniated electrons. [CaO, CaCO3 and Ca(OH)2] are bases and hence dissolve in
4. Here sodium formate is formed as follows acetic acid.
200OC 56. Mg2+ has a smaller size than Na+ and thus has higher hydra‑
NaOH + CO HCOONa
tion energy than Na+.
5. Here hypo is formed as follows 3300 K
Δ 57. CaO + 3C CaC2 + CO
Na2SO3 + S Na2S2O3
58. Limestone (CaCO3) is not required in the manufacture of P
7. K2CO3 + 2C 2K + 3CO from phosphorite.
8. KClO4 + H2SO4 KHSO4 + HClO4 59. MgCl2 hydrolyzes to give HCl. So the pH of the solution will
Perchloric acid be < 7.
9. As potassium reacts very violently with water giving hydro‑ 60. A solution of calcium in liquid ammonia on evaporation
gen so intensity of fire increases. gives Ca(NH3)6 as residue.
10. It is a reducing agent because of the presence of sodium. 65. Carnalite (MgCl2 KCl.6H2O) is an ore of Mg which on elec‑
11. Sodium amalgam is an alloy of Na and Hg. It is a mixture so trolysis gives Mg at the cathode and Cl2 at the anode.
sodium is in metallic state. Hence its oxidation state is zero. 71. Dead burnt plaster is anhydrous CaSO4
12. Group IA elements are good reducing agents. 72. Na2CO3 + 2H2O 2NaOH + H2O + CO2
13. Main ingredients are NH3, NaCl solution and CO2. 2NaOH + 2Al + 2H2O 2NaAlO2 + 3H2
14. High blood pressure is caused by taking excess of Na+ ions Soluble
in the diet. 74. AlCl3 + 3NH4OH Al(OH)3 + 3NH4Cl
15. Na2O2 and HCl mixture is called oxone. 75. AlN + 3HCl AlCl3 + NH3
16. K2O + H2O 2KOH. 78. Al2O3 + 6Na 2Al + 3Na2O
17. In NaCl crystal, Na+ and Cl– ions due to strong attractive Sodium oxide
forces are not free to move. 80. Al2O3 + 3C + 3Cl2 2AlCl3 + 3CO
19. Sodium in excess of oxygen forms Na2O2. 81. Alnico an alloy of aluminium and nickel, cobalt and iron is
23. BaSO4 + Na2CO3 BaCO3 + Na2SO4 used in making magnets for hearing aids.
26. Na2CO3 is a salt of weak acid and strong base. So its aqueous 82. Emery is an abrasive having impure corundum and used for
solution is alkaline due to hydrolysis of CO32– ions. polishing and grinding.
27. In ammonia soda process, the by‑products obtained are 86. KHC4H4O6 is potassium hydrogen tartarate and used to
CaCl2, CO2 and NH3. transform baking soda into baking powder.
Δ 87. 2NaOH + CO2 Na2CO3
28. 2Na + 2NH3 2NaNH2 + H2
Solid
29. In NaCl (rock salt) structure, Cl– ions form FCC type of
88. Here KCN is formed as follows
lattice.
K4 [Fe(CN)6] + K2CO3 5 KCN
30. Al(OH)3 formed as white precipitate gets dissolves in excess
+ KCNO + Fe + CO2
of NaOH to form soluble NaAlO2.
Δ 89. 2NaOH + CO2 Na2CO3 + H2O this reaction is not
32. 2 NaNO3 2NaNO2 + O2 associated with Solvay process.
43. KCl MgCl2 6H2O K+, Mg2+, 3Cl– So K+, Mg2+, 90. H+ ions are discharged at a higher potential when Hg cathode
–
Cl ions give positive tests. is used, than that using Pt cathode.
44. Mixture of calcium dihydrogen phosphate and gypsum is 92. Here purple colour is due to formation of sodium pentacy‑
known as calcium super phosphate. ano nitrosylferrare (II) which is formed as follows
51. Carnalite is KCl.MgCl2.6H2O. It is an ore of Mg. Na2S + Na2[(Fe) (NO) (CN)5].2H2O
53. Plaster of paris, CaSO4. ½ H2O is used in dentistry and surgery.
Na3 [Fe (CN)5 NOSNa]
54. Ca(OH)2 + Cl2 CaOCl2 + H2O Heat
Bleaching powder 93. Al2(SO4)3.18H2O Al2(SO4)3
–18H2O
Bleaching powder is a mixed salt of calcium hypochlorite, (A)
800OC
Ca(OCl)2 and basic calcium chloride, CaCl2. Ca(OH)2.H2O. Al2O3 + 3SO3
(B) (C)
 Chemistry of Lighter Elements 17.27

94. A and B are CO2 and CO2. (B) (C)

(a) CO2 CO2
Ca(OH)2 CaCO3↓ 2Na2S2O3 + I2 Na2S4O6 + 2NaI
Δ H2O (C) (D)
Δ
Ca(HCO3)2 CaCO3 + CO2 ↑ 119. CaCOCl2 + H2O Ca(OH)2 + Cl2
(Soluble) (ppt.) (B)
As2O2 + 2Cl2 +2H2O As2O3 + 4HCl
96. Magnesium wire reduce CO2 to C
Meq = Meq Cl2
2Mg + CO2 2MgO + C mol. wt. 198
Eq. wt. of As2O3 = = = 49.5
97. Halides of group 2 elements are hygroscopic and act as 4 4
dehydrating agents. N = 4.3
49.5
99. Na + (x + y) NH3 [Na(NH3)x]+ + [e (NH3)y]– Thus, Total Meq of arsenite used
due to solvated (ammoniated) electron, solution of Na metal §  · 
in liquid ammonia is highly reducing in nature. = ¨ u u = Meq Cl2
©  ¹̧ 
Δ
102. Na2CO3 .10H2O Na2CO3.H2O
–9H2O  u 
Δ Meq Cl2 =
Na2CO3 + H2O 
 
uu
2+
104. Test of Mg ion g of Cl2 = 13.4 × = 0.33
Mg2+ + NH4OH + Na2HPO4 Mg(NH4)PO4  
Magnesium ammonium 
Percentage of Cl2 = × 100 = 31.7%
phosphate 
105. Here anion of sodium salt must be HCO3– and the reactions 120. BaCO3 + 2HCl BaCl2 + H2O + CO2
are (A) (C) (B)
MgCl2 + 2NaHCO3 Mg(HCO3)2 + 2NaCl H2SO4
BaCl2 BaSO4 + 2HCl
Soluble (D)
Δ
Mg(HCO3)2 MgCO3 + H2O + CO2 K2CrO4
White BaCrO4 ↓ + 2KCl
106. These loose electrons absorb radiation and then radiate it (E)
back. CaCO3 + H2O + CO2 Ca(HCO3)2
Clear solution
108. When HE > LE the salt is soluble in water.
121. AlCl3 + 3NH4OH Al(OH)3 + 3NH4Cl
109. Zn2+ + 2NaOH 2Na+ + Zn(OH)2
Al(OH)3 + NH4OH No reaction
Zn(OH)2 + 2NaOH Na2ZnO2 + 2H2O
AlCl3 + 3AgNO3 3AgCl + Al(NO3)3
Thus Na2ZnO2 forms 2Na and [ZnO2]2– ions.
+
White precipitate
110. H+ has greater mobility than Na+, because of its smaller 123. Fluorspar is added in small quantities in the electrolytic
size as compared with Na+, therefore electrode potential (or reduction of alumina dissolved in fused cryolite (Na3AlF6).
reduction potential) of H+ (0.00 V) is greater than that of Na+
1. To make the fused mixture more conducting as alumina is
(–2.17 V). Hence H+ is reduced in preference to Na+.
a bad conductor of electricity.
At cathode: 2H+ (aq) + 2e– H2 (g) 2. To lower the melting point of the fused mixture to 1140
111. 2Al + 3H2SO4 Al2(SO4)3 + 3H2 K. Alumina has a high melting point of 2323 K.
2Al + 2NaOH + 2H2O 2NaAlO2 + 3H2 125. Acidic and basic salts do not exist together in aqueous solu‑
So, the ratio of volumes of hydrogen evolved is 1 :1. tion because they react.
115. Due to efflorescence (to give out H2O) nature of 2NaOH + NaH2PO4 Na3PO4 + 2H2O
Na2CO3.10H2O. NaHCO3 + NaOH Na2CO3 + H2O
116. Al(OH)3 + OH– [Al(OH)4–] 127. NaCl + 2NH3 + CO2 + H2O NaHCO3 + NH4Cl
coordination number is 6, thus it exists as [Al (H2O)2 (OH)4]–. (A)
Δ
117. Al(OH)3 is a gelatinous white precipitate, formed by the 2NaHCO3 Na2CO3 + H2O + CO2
reaction of Al3+ with NH4OH in the presence of NH4Cl. (B)
H 2O
118. Na2CO3 + SO2 2NaHSO3 + CO2 CO2 + Ca(OH)2 CaCO3 + H2O
(A) Δ
129. 3Mg + N2 Mg3N2
2NaHSO3 + Na2CO3 2Na2SO3 + H2O + CO2 (X) (Y)
(A) (B) Mg3N2 + 6H2O 3Mg(OH)2 + 2NH3
Δ
Na2SO3 + S Na2S2O3 (Y) Colourless
17.28 Chapter 17

CuSO4 + 4NH3 [Cu(NH3)4]SO4 131. Mg and Al are more electropositive than hydrogen and hence
Blue complex cannot be obtained by electrolysis of the aqueous solution of
130. A highly pure, dilute solution of sodium in liquid ammonia their salts.
is blue in colour, due to ammoniated electron. This solution 132. Na2Al2Si2O8.xH2O is written as Na2Z, Na+ ions exchange
is conducting, due to the presence of both ammoniated cat‑ Ca2+ and Mg2+ ions in hard water.
ion and ammoniated electron. Na2Z + Mg2+ 2Na+ + MgZ
Na + (x + y)NH3 [Na(NH3)x]+ + [e (NH3)y]– Na2Z + Ca 2+
2Na+ + CaZ

More than One Option Correct Type

139. Acidic and basic salts do not exist together in aqueous solu‑ NaHCO3 + NaOH → Na2CO3 + H2O
tion because they react.
142. When H.E. > L.E. the salt is soluble in water.
2NaOH + NaH2PO4 → Na3PO4 + 2H2O

Passage Based Questions

Passage-2 Passage-3

153. 3Ca + N2 → Ca3N2 155. (X) is NaHCO3 (molecular wt. = 84)

Δ
(A) (B), Calcium nitride 156. 2NaHCO3 Na2CO3(s) + CO2(g) + H2O(g)
(An ionic compound) (X) (Y) (A) (B)
2 x 84 = 168g 106 g 44 g 18 g
Ca3N2 + 6H2O → 3Ca(OH)2 + 2NH3 ≈ 16.8 g 10.6 g 4.4 g 1.8 g
(C) (D) CO2 + Ca(OH)2 → CaCO3 → + H2O
Lime water white ppt.
Calcium hydroxide
H2O (g) is condensed to liquid water
154. As calcium can form complexes only with strong complex‑ 157. Na2CO3 + BaCl2 → BaCO3 + NaCl
ing agents like EDTA (Y) (Z)
BaCO3 + 2HCl → BaCl2 + H2O + CO2
(Z)

Previous Years' Questions

163. 4KO2 + 2CO2 2K2CO3 + 3O2 169. Be (Z = 4) has maximum covalency of 4 while Al (Z = 13)
164. M is Be which forms water soluble BeSO4, water insolu‑ has maximum covalency of 6. \
ble Be(OH)2 and BeO. Be(OH)2 is soluble in NaOH giving 171. CaCO3 
∆
→ CaO + CO 2
Basic oxide
sodium beryllate Na2BeO2. acidic oxide

167. Calcined gypsum does not contain CaCO3 whereas all other
materials contain CaCO3 in them.