S – block elements - I

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01. Among the following halides for which one H f is more negative?
a) LiF b) NaF c) RbF d) CsF
02. In KO 2 , the nature of oxygen species and the oxidation state of oxygen atom are, respectively
1 1
a) Oxide and – 2 b) Superoxide and  c) Peroxide and  d) Superoxide and – 1
2 2
03. Which of the following statements is correct regarding S-block elements?
a) Superoxide of alkali metals are black in colour
b) CsI is less soluble in water due to high covalent character
c) On heating LiNO3 gives a brown gas
d) Oxide and hydroxide of Be are acidic in nature
04. A metal ‘M’ reacts with N 2 to from 'M 3 N' . 'M 3 N' on heating at high temperature gives back ‘M’ and
on reaction with water produces gas ‘C’. Gas ‘B’ reacts with aq.solution of CuSO 4 to form a deep blue
compound. ‘M’ and ‘B’ respectively are
a) Li and NH 3 b) Al and N 2 c) Ba and N 2 d) Na and NH3
05. The metal that forms nitride by reacting directly with N 2 of air, is
a) Cs b) Li c) Rb d) K
06. Sodium metal on dissolution in liquid ammonia gives a deep blue solution due to the formation of
a) ammoniated electrons b) Sodium – ammonia complex
c) sodium ion- ammonia complex d) Sodamide
07. A metal on combustion in excess air form ‘X’. ‘X’ upon hydrolysis with water yields H 2O 2 and O 2
along with another product. The metal is
a) Na b) Rb c) Li d) Mg
08. Choose the correct statement(s) regarding alkali metals?
a) Except ‘Li’ all form carbide on heating with carbon
b) Except ‘Li’ all form acetylide on reaction with acetylene
c) Except ‘Li’ all form nitride on heative with nitrogen
d) Except ‘Li’ all can be stored in kerosene
09.Potassium on burning in air form compound ‘x’. ‘x’ on hydrolysis forms a solution and releases a gas.
How many anti bonding electrons are present in the gas
10. Which of the following statements are true about the alkalie metals
a) All alkali metal salts impart a characteristic colour to the Bunsen flame
b) Among LiaOH, CsOH, KOH and RbOH; CsOH has the highest solubility in water
c) Among the alkali metals, Cs is the most reactive
d) The reducing character of the alkali metal hydrides follow the order: LiH>NaH>KH > RbH > CsH
11. Propert(ies) of all the alkali metals that increase(s) with their atomic number is (are)
a) Solubility of their hydroxides b) Thermal stability of their carbonates
c) Softness d) Hydration energy
12. Which of the following statements is / are true?
a) Both LiCl and MgCl 2 are deliquescent
b) Li is least reactive but the strongest reducing agent in aq.solution amongst all the alkali metals
c) Liquid Na metal is used as a coolant in fast breeder nuclear reactors
d) LiI is the most ionic in nature among alkali metal halides
13. Highly pure dilute solution of sodium in liquid ammonia
a) On evaporation yield metal b) Exhibit electrical conductivity
c) Produces sodium amide and H 2 gas instantly d) Acts as powerful reducing agent
14. Pick up the correct statements regarding alkali metals?
a) Density: Cs > Rb > Na > K > Li
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b) Strongest and weakest reducing agents based on E values among alkali metals are Li and Na
M / M
respectively
    
c) Hydration enthalpy: Li  Na  K  Rb  Cs
d) Stability of suporoxides: KO 2  RbO2  CsO2
15. The main oxides formed on combustion of Li, Na and K in excess of air are respectively
a) Li 2O, Na 2O 2 and KO 2 b) Li 2O, Na 2O and KO 2
c) LiO2 , Na 2O 2 and KO2 d) Li 2O2 , Na 2O2 and KO 2
16. Select the incorrect statement about Na in liquid NH 3 in dilute condition?
a) Solution is paramagnetic
b) Solution is a good conductor due to solvated ion and solvated electron
c) Solution is blue in colour d) Solution is strong oxidizing agent
17. Which is not correctly matched?
a) Cs 2O  Rb 2O  K 2O  Na 2O  Li 2O  Basic nature of oxides
2   
b) Be  Li  Na  K  mobility of hydrate ions
c) LiHCO 3  NaHCO 3  KHCO3  RbHCO3  CsHCO 3  thermal stability
d) NaF < NaCl < NaBr < NaI – M.P
18. Which of the following statement is false for alkali metals?
a) Bicarbonate of Li is not known is solid state
b) Li react less vigorously with water than Na
c) Li has least SRP where as Rb ha highest
d) All dissolve in liquid ammonia giving paramagnetic deep blue solution
19. Which of the following order is correct w.r.t magnitude of cuthalpies of formation of alkali metal
halides?
a) Iodide > Bromide > Chloride > Fluoride (Same metal) b) CsCl > RbCl > NaCl > LiCl
c) NaF> CsF > RbF > KF d) LiI > NaI > RbI > CsI
20. Which of the statement is correct?
a) Li, when burnt in air, gives monoxide, peroxide and superoxide
b) On heating Li 2CO3 ,Li 2O and CO 2 are formed
c) Among alkali metals, Li metal has high I.E. and impart no colour to flame
d) Li 2SO 4 forms alum
21. Select the alkali metals having highest density and melting point, respectively
a) Li,Li b) Li, Cs c) Cs, Li d) Cs, Cs
22. Which of the following two compounds of potassium evolve gases when react with water?
a) KNO3 and K 2CO3 b) KO 2 and K 2S
c) KHCO3 and KOH d) K 2O 2 and K 2SO4
23. The first and second ionization enthalpies of a metal are 496 and 4560 kJ / mol respectively, How many
moles of HCl and H 2SO 4 , respectively, will be needed to react completely with 1 mole of the metal
hydroxide?
a) 1 and 0.5 2) 2 and 0.5 c) 1 and 1 d) 1 and 2
24. Among the statement (a) – (d), the correct ones are
I) Lithium has the highest hydration enthalpy among the alkali metals
II) LiCl is insoluble in pyridine
III) Lithium cannot form ethynide upon its reaction with ethyne
IV) Both Li and Mg react slowly with H 2O
a) I, II and IV only b) II and III only c) I, III and IV only d) I and IV only
25. Select the incorrect statement about Na in liquid NH 3 in dilute condition
a) Solution is paramagnetic
b) Solution is a good conductor due to solvated ion and solvated electron
c) Solution is blue in colour
d) solution is strong oxidizing agent
26. Which is not true about the reaction of KO 2 with CO 2 and H 2 O
a) In KO 2 , oxidation number of K is +1 b) KO 2 acts as reductant
c) KO2 acts as oxidant d) Oxidation number of carbon does not change during the reaction
27. Total number of moles of O 2 produced for breathing if the mask contains 3.5 gm of dry KO 2 ? (Aw of
K =30)
a) 0.037 b) 0.027 c) 0.017 d) 0.047
28. Sesqui oxide K 2O 3 is prepared by careful thermal decomposition of KO 2 .K 2O 3 contains
a) K with + 1 oxidation state b) Paramagnetic anion(s)
c) K 2O 2 and KO 2 in 1: 2 ratio d) Produce O 2 on decomposition
29. Select correct statement(s)?
a) Oxides and peroxides of alkali metals are diamagnetic b) Superoxides of A.M’s are paramagnetic
c) Lithium do not form superoxides d) Superoxides of A.M’s are colourless
30. How many moles of CO2 are formed when an equimolecular mixture of Li 2CO 3 and K 2CO 3 is
heated?
31. How many of the following yield paramagnetic species? Na and excess of NH 3 , K and excess of O2
excess of NaOH and ZnCl 2

32. Number of HCO3 ions joined by hydrogen bonding in KHCO3 is____
33. Which of the following does not illustrate the anomalous properties of Lithium?
a) Li is much softer than the other group first metals
b) The MP and BP of Li are comparatively high
c) Li form a nitride Li3 N unlike group first metals
d) The ions of Li and its compounds are more heavily hydrated than those of the rest of the group first
elements
34. Alkali metals acts
a) Good dehydrating reagent b) Good reducing agent
c) Good oxidizing agent d) None of these
35. the substance ‘x’ belonging to IA group gives a pale violet colour in flame test, x is
a) NaCl b) CsCl c) KCl d) LiCl
36. Which of the following increases in magnitude as the atomic number of alkali metals increases?
a) Electronegativity b) First ionization energy c) Ionic radius d) Melting point
37. The main oxides formed on combustion of Li, Na and K in air are respectively
a) Li 2O, Na 2O 2 and KO 2 b) Li 2O, Na 2O and KO 2
c) LiO 2 , Na 2O 2 and KO 2 d) Li 2O 2 , Na 2O 2 and KO 2
KEY
01. a 02. 03. C 04.a
05. b 06.a 07.b 08.b,d
09.6 10. Abc 11.a,b,c 12.a,b,c
13. a,b,d 14.abcd 15.a 16.d
17. a,d
18.c
Sol:
Metal: Li Na K Rb Cs
E 0
: -3.04V - 2.714 V - 2.925 V - 2.93 V - 2.927 V
M / M
19. b

Sol:
M(Alkali metal) MF HCl MBr MI
Li - 612 - 398 - 350 - 271
Na - 569 - 400 - 360 - 288
K - 563 - 428 - 392 - 328
Rb - 549 - 423 - 389 - 329
Cs - 531 - 424 - 395 - 337
20. b 21.c
22. b
Sol: KO 2  H 2O  KOH  H 2O 2  O 2 ; K 2S  H 2O  KOH  H 2S
23. a 24.c 25.d
26. c
1
Sol: KO 2  2H 2O  KOH  H 2O 2  O2
2
4KO 2  2H 2O  2K 2CO3  3O 2
excess CO 2
4KO2  4CO2  2H 2O   4KHCO3  3O 2
27. a
Sol: 4KO 2  2CO 2  2K 2CO3  3O 2
4  7gm ____________________ 3m res
3.5  3
3.5gm ____________________ 2   0.0369
4  71
28. a,b,c,d 29.abc 30.1 31.2
32. 2 33.a 34.b 35.c
36. c 37.a