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Important Questions
10th Standard
Science
10th std Science
Important questions
Part - A 50 x 1 = 50
1) Which of the following has the smallest mass?
(a) 6.023 × 1023 atoms of He(b) 1 atom of He(c) 2 g of He(d) 1 mole atoms of He
2) Which of the following is a triatomic molecule?
(a) Glucose(b) Helium(c) Carbon dioxide(d) Hydrogen
3) Th e volume occupied by 4.4 g of CO2 at S.T.P
(a) 22.4 litre(b) 2.24 litre(c) 0.24 litre(d) 0.1 litre
4) Mass of 1 mole of Nitrogen atom is
(a) 28 amu(b) 14 amu(c) 28 g(d) 14 g
5) Which of the following represents 1 amu?
(a) Mass of a C – (b) Mass of a (c) 1/12th of the mass of a C (d) Mass of O –
12 atom hydrogen atom – 12 atom 16 atom
6) The mass of an atom is measured in ____________
(a) kg(b) amu(c) g(d) Pm
7) Atoms of different elements with different atomic numbers, but same mass number are
known as _________
(a) isobars(b) isotopes(c) isotones(d) isomers
8) Pick out the isotopes among the following pairs
(a) 6C13, 7N14 (b) 18Ar4, 20Ca4 (c) 6C12, C614(d) 5B12, 6C13
9) Which among the following is a homo atomic molecule?
(a) N2 (b) NH3 (c) HCl(d) N2O
10) Identify the 'hetero nuclear tri atomic molecule' among the following.
(a) P4(b) H2SO4 (c) CO2 (d) O3
11) The number of periods and groups in the periodic table are__________.
(a) 6,16(b) 7,17(c) 8,18(d) 7,18
12) The basis of modern periodic law is__________
(a) atomic number(b) atomic mass(c) isotopic mass(d) number of neutrons
13) _____ group contains the member of halogen family.
(a) 17th(b) 15th(c) 18th(d) 16th
14) _____ is a relative periodic property
(a) atomic radii(b) ionic radii(c) electron affinity(d) electronegativity
15) Chemical formula of rust is ________.
(a) FeO.xH2O(b) FeO4.xH2O(c) Fe2O3.xH2O(d) FeO
16) Which of the following is the pair of shortest and longest periods in the modern
periodic table?
(a) 1st, 2nd (b) 2nd,3rd(c) 5th, 7th(d) 1th,6th
17) Pick the correct order on decreasing trend of atomic size
(a) Mg, Mg+, Mg2+(b) Mg+,Mg2+,Mg(c) Mg2+,Mg+,Mg(d) Mg2+,Mg, Mg+
18) Among the halogens which one is most electro-negative?
(a) Iodine(b) Chlorine(c) Bromine(d) Fluorine
19) The acid which makes iron passive is _______________
(a) Conc.HCl(b) Cone.H2SO4 (c) Cone.HNO3 (d) Cone.HF
20) The green layer found on the copper vessel is due to the formation of ________
(a) basic copper carbonate(b) cupric oxide(c) cuprous oxide(d) copper chloride
21) A solution is a __________ mixture.
(a) (b) (c) homogeneous and (d) non
homogeneous heterogeneous heterogeneous homogeneous
22) The number of components in a binary solution is _____________
(a) 2(b) 3(c) 4(d) 5
23) Which of the following is the universal solvent?
(a) Acetone(b) Benzene(c) Water(d) Alcohol
24) A solution in which no more solute can be dissolved in a definite amount of solvent at a
given temperature is called ___________
(a) Saturated (b) Un saturated (c) Super saturated (d) Dilute
solution solution solution solution
25) Identify the non aqueous solution.
(a) sodium chloride in (b) glucose in (c) copper sulphate in (d) sulphur in carbon-di-
water water water sulphide
26) Sugar and copper sulphate crystals are dissolved in water. The solution is called as
(a) binary(b) trinary(c) ternary(d) quartenary
27) 40 g of sodium chloride in 100 g of water at 250 C forms ________ solution.
(a) Super saturatedUnsaturated(b) Unsaturated(c) Saturated(d) Both (a) and (b)
28) 8% of NaCI solution is
(a) 8g of NaCl in 100 (b) 8 g of NaCl in 92 (c) 92 g of NaCl in 8 (d) 92 g of NaCl in 100
g of water g of water g of water g of water
29) White vitriol is ________
(a) CaSO4·7H2O(b) MgSO4.7H2O(c) K2SO4.7H2O(d) ZnSO4.7H2O
30) Anhydrous copper sulphate is _______ in colour.
(a) blue(b) bluish green(c) colourless(d) black
31) H2(g) + Cl29(g) → 2HCl(g) is a
(a) Decomposition (b) Combination (c) Single Displacement (d) Double Displacement
Reaction Reaction Reaction Reaction
32) Photolysis is a decomposition reaction caused by
(a) heat(b) electricity(c) light(d) mechanical energy
33) The reaction between carbon and oxygen is represented by C(s) + O2(g) → CO2(g) + Heat. In
which of the type(s), the above reaction can be classified?
(i) Combination Reaction
(ii) Combustion Reaction
(iii)Decomposition Reaction
(iv) Irreversible Reaction
(a) i and ii(b) i and iv(c) i, ii and iii(d) i, ii and iv
34) The chemical equation Na2SO4(aq) + BaCl2(aq) → BaSO4(s)↓ + 2NaCl(aq) represents which of
the following types of reaction?
(a) Neutralisation(b) Combustion(c) Precipitation(d) Single displacement
35) A single displacement reaction is represented by X(s) + 2HCl(aq) → XCl2(aq) + H2(g). Which
of the following(s) could be X. (i) Zn (ii) Ag (iii) Cu (iv) Mg. Choose the best pair.
(a) i and ii(b) ii and iii(c) iii and iv(d) i and iv
36) Which of the following information is not conveyed by a balanced chemical equation?
(a) Physical states(b) Symbols and (c) Number of atoms / (d)
of reactants and chemicals formula of molecules of the Feasibilityof a
products reactants and products reactants and products chemical
formed reaction
37) The product formed when calcium oxide reacts with water is
(a) Slaked lime(b) Carbon dioxide(c) Calcium oxide(d) Oxygen gas
38) The reaction between hydrogen and oxygen gas to form water is __________________
(a) combination(b) redox(c) exothermic(d) all of these
39) An element 'A' on exposure to moist air turns to form compound 'B' which is reddish
brown. Identify 'A'.and 'B'
(a) 'A' is Ag, 'B' is (b) 'A' is Cu, 'B' is (c) 'A' is Mg, 'B' is (d) 'A' is Fe, 'B' is
Ag2s CuO MgO Fe2O3
40)
The above thermal decomposition reaction is an ___________ reaction.
(a) endothermic(b) exothermic(c) both (a) and (b)(d) neither (a) nor (b)
41) The molecular formula of an open chain organic compound is C3H6. The class of the
compound is
(a) alkane(b) alkene(c) alkyne(d) alcohol
42) The IUPAC name of an organic compound is 3-Methyl butan-1-ol. What type compound
it is?
(a) Aldehyde(b) Carboxylic acid(c) Ketone(d) Alcohol
43) The secondary suffix used in IUPAC nomenclature of an aldehyde is ____
(a) - ol(b) – oic acid(c) – al(d) - one
44) Which of the following pairs can be the successive members of a homologous series?
(a) C3H8 and C4H10 (b) C2H2 and C2H4(c) CH4 and C3H6(d) C2H5OH and C4H8OH
45) C2H5OH + 3O2 → 2CO2 + 3H2O is a
(a) Reduction of (b) Combustion of (c) Oxidation of ethanoic (d) Oxidation of
ethanol ethanol acid ethanal
46) Cyclobutane is an example of ______________ compounds.
(a) a cyclic(b) cyclic(c) aromatic(d) alicyelic
47) General molecular formula of alkynes is ___________.
(a) CnH2n+2(b) CnH2n(c) CnH2-n-2 (d) CnH2n+1
48) Ethene is an ___________
(a) alkane(b) alkene(c) alkyze(d) armatic hydrocarbon
49) Methylene group is
(a) CH4(b) - CH3 (c) - CH2 -(d) - CH -
50) Identify the ketone among the following
(a) CH3COCH3(b) CH3CHO(c) CH3COOH(d) CH3COOCH3
Part - B 25 x 2 = 50
51) Define : Relative atomic mass.
Answer : The Relative Molecular Mass of a molecule is the ratio between the mass of one
molecule of the substance to 1/12th mass of an atom of Carbon - 12.
52) Write the different types of isotopes of oxygen and its percentage abundance
Answer : Oxygen exists as a mixture of three stable isotopes in nature.
IsotopeMass (amu) % abundance
16
8O 15.9949 99.757
17
8O 16.999 0.038
18
8O 17.9992 0.205
53) Define atomic mass unit?
Answer : Atomic mass unit is one - twelfth of mass of carbon - 12 atom, an isotope of
carbon which contains 6 protons and 6 neutrons.
54) Measurement of atomic mass of an element is very difficult? Give reason.
Answer : (i) Measurement of atomic mass of an element is somewhat more complicated
since most of the elements exist as a mixture of isotopes, each of which has its own
mass.
(ii) Thus, it is essential to consider this isotopic mixture while calculating atomic mass of
an element.
55) Define average atomic mass (AAM).
Answer : The average atomic mass of an element is the weighted average of masses of its
naturally occurring isotopes.
56) A is a reddish brown metal, which combines with O2 at < 1370 K gives B, a black
coloured compound. At a temperature > 1370 K, A gives C which is red in colour. Find
A,B and C with reaction.
Answer : Reddish brown metal A is copper
below
Copper(II) oxide abave
Copper (1) oxide (red)
2C u ⟶ 2C u o 4C u + O 2 ⟶ 2 C u2 O
(A) 1370k (B) 1370k (C )
A -Cu -Coper
B-CuO -Copper (II) oxide
C-Cu2O-Coper I oxide
57) A is a silvery white metal. A combines with O2 to form B at 800oC, the alloy of A is used
in making the aircraft. Find A and B
Answer : Silvery white metal is aluminium
0
800 C
4Al + 3O2 ⟶ 2Al2 O 3 (B)
A Al Aluminium
BAl2O3 Aluminium oxide
58) Define Modern periodic law.
Answer : "The physical and chemical properties of the elements are the periodic
functions of their atomic numbers".
59) Define periodicity.
Answer : The repetition of properties of the elements in regular intervals is called
periodicity.
60) Classify the 32 elements present in 6th period.
Answer : Sixth period contains 32 elements (Casesium to Radon) includes 8 normal
elements, 10 transition elements and 14 inner transition elements (Lanthanides).
61) Define the term: Solution
Answer : Solution is a homogeneous mixture of one or more substances.
62) What is mean by binary solution
Answer : Solutions which are made of one solute and one solvent (two components) are
called binary solutions.
63) Define a solute and a solvent.
Answer : In a solution, the component which is present in lesser amount (by weight), is
called solute and the component, which is present in a larger amount (by weight) is called
solvent.
64) Define dissolution.
Answer : The process of uniform distribution of solute into solvent is called dissolution.
65) What is super saturated solution? Give an example.
Answer : Supersaturated solution is one that contains more solute than the saturated
solution at a given temperature. E.g. 40 g of sodium chloride in 100 g of water at 250 C
forms super saturated solution.
66) When an aqueous solution of potassium chloride is added to an aqueous solution of
silver nitrate, a white precipitate is formed. Give thr chemical equation of this reaction
Answer : KCI + AgNO3 ⟶ KNO3 + AgCI↓
67) Why does the reaction rate of a reaction increase on raising the temperature?
Answer : Increase in temperature provides energy to break more bonds and thus speeds
up the reaction.
68) Define rate of reaction.
Answer : "Rate of a reaction is the change in the amount or concentration of anyone of
the reactants or products per unit time".
Consider the following reaction
A⟶B
The rate of this reaction is given by
Rate = d[A]
= +
d[B]
dt dt
Where,
[A] - Concentration of A
[B] - Concentration of B
69) Identify whether the following reaction is reversible or irreversible
Answer : (i) Combustion of coal ⟶ Irreversible reaction
(ii) Decomposition of PCl5 ⟶ Reversible reaction
70) Define endothermic reaction. Give an example.
Answer : Reactions in which heat is absorbed are called 'Endothermic reactions'.
71) Name the simplest ketone and give its structural formula.
Answer : Simplest Ketone is acetone
Structural formula - CH3COCH3
72) Classify the following compounds based on the pattern of carbon chain and give their
structural formula: (i) Propane (ii) Benzene (iii) Cyclobutane (iv) Furan
Answer :
(i) Propane acyclic CH3COCH3
(ii) Benzene Cyclic Aromatic Compound
(iii) Cyclo butaneAlicyclic
(iv) Furan Hele Trocyclic
73) What are hydrocarbons?

Answer : The organic compounds that are composed of only carbon and hydrogen atoms
are called hydrocarbons.
74) Write a test to alkanes from alkenes.
Answer : (i) Unsaturated compounds like alkenes decolourise bromine water.
(ii) Saturated compounds like alkanes do not decolourise bromine water
75) What is rectified spirit??

Answer : Aqueous solution of ethanol which contain 95.5% of ethanol and 4.5% of water
is called rectified spirit.
Part - C 20 x 4 = 80
76) Calculate the number of water molecule present in one drop of water which weighs 0.18
g.
Answer : Mass of water = 0.18 g
No of moles = M ass
M olecular M ass
= 0.18
= 0.01 mole
Number of molecules = No of moles x Avogadro number
= 0.01 x 6.023 x 1023
= 0.06023 X 1023
= 6.023 X 1021molecules
77) N2 + 3 H2 → 2 NH3
(The atomic mass of nitrogen is 14, and that of hydrogen is 1)
1 mole of nitrogen (_______g) +
3 moles of hydrogen ( _________ g) →
2 moles of ammonia ( _________ g)
Answer : 28, 6, 34
78) Give the applications of Avogadro's hypothesis.
Answer : Applications of Avogadro's hypothesis
(i) It explains Gay- Lussac's law.
(ii) It helps in the determination of atomicity of gases.
(iii) Molecular formula of gases can be derived using Avogadro's law.
(iv) It determines the relation between molecular mass and vapour density.
(v) It helps to determine Gram molar volume of all gases (i.e, 22.4 lit at S.T.P)
79) a) State the reason for addition of caustic alkali to bauxite ore during purification of
bauxite.
b) Along with cryolite and alumina, another substance is added to the electrolyte mixture.
Name the substance and give one reason for the addition
Answer : (a) Caustic soda solution at 1500 is added to bauxite ore to obtain Sodium
Meta Aluminate.
(b) Fluorspar is added to the electrolyte mixture so as to lower the fusion temperature of
the electrolyte.
80) Explain the salient features of periods in the modern periodic table.
Answer : Features periods:
(i) The horizontal rows are called periods. There are seven periods in the periodic table.
(ii) First period (Atomic number 1 and 2): This is the shortest period. It contains only two
elements (Hydrogen and Helium).
(iii) Second period (Atomic number 3 to 10): This is a short period. It contains
eight elements (Lithium to Neon).
(iv) Third period (Atomic number 11 to 18): This is also a short period. It contains
eight elements (Sodium to Argon).
(v) Fourth period (Atomic number 19 to 36): This is a long period. It contains
eighteen elements (Potassium to Krypton). This includes 8 normal elements and
10 transition eIements.
(vi) Fifth period (Atomic number 37 to 54): This is also a long period. It contains
18 elements (Rubidium to Xenon). This includes 8 normal elements and 10 transition
elements.
(vii) Sixth period (Atomic number 55 to 86): This is the longest period. It contains 32
elements (Caesium to Radon). This includes 8 normal elements, 10 transition elements
and 14 inner transition elements (Lanthanides).
(viii) Seventh period (Atomicnumber 87to 118): Like the sixth period, this period also
accommodates 32 elements. Recently 4 elements have been included by IUPAC.
81) Explain the salient features of groups in the modern periodic table.
Answer : (i) The vertical columns in the periodic table starting from top to bottom are
called groups. There are 18 groups in the periodic table.
(ii) As the elements present in a group have identical valence shell electronic
configurations, they possess similar chemical properties.
(iii) Vertical columns in the periodic table starting from top to bottom are called groups.
There are 18 groups in the periodic table.
(iv) The Lanthanides and Actinides which form part of Group 3 are called inner transition
elements.
(v) Except group 0, all the elements present in each groups have same valency. The
elements present in a group possess similar chemical properties.
(vi) The physical properties of the elements in a group such as melting point, boiling point
and density vary gradually.
(vii) The atoms of the group 0 elements have stable electronic configuration in their
valence shells and hence they are unreactive.
82) How will you predict the nature of chemical bonds using electronegativity values?
Answer : (i) If the difference in electronegativity between the two elements is 1.7, the
bond has 50% ionic character and 50% covalent character.
(ii) If the difference is less than 1.7, the bond is considered to be covalent.
(iii) If the difference is greater than 1.7, the bond is considered to be ionic.
83) Write notes on various factors affecting solubility
Answer : There are three main factors which govern the solubility of a solute. They are:
Nature of the solute and solvent, Temperature, Pressure
Nature of the solute and solvent :
(i) The nature of the solute and solvent plays an important role in solubility.
(ii) Solubility is based on the phrase "like dissolves like:" The expression means that
dissolving occurs when similarities exist between the solvent and the solute. For example:
Common salt is a polar compound 4 and dissolves readily in polar solvent like water.
(iii) Non-polar compounds are soluble in non-polar solvents. For example: Sulphur
dissolves in carbon disulphide.
Effect of Temperature :
Solubility of Solids in Liquid:
(i) Generally, solubility of a solid solute in a oS liquid solvent increases with increase
in temperature.
(ii) In endothermic process, solubility increases with increase in temperature.
(iii) In exothermic process, solubility decreases with increase in temperature.
Solubility of Gases in liquid: Solubility of gases in liquid decrease with increase in
temperature.
Effect of Pressure : When the pressure is increased, the solubility of a gas in liquid
increases. When pressure is increased, more gas molecules strike the surface of the
liquid and mix into the solution.
84) a) What happens when MgSO4.7H2O is heated? Write the appropriate equation
b) Define solubility
Answer : (i) When magnesium sulphate heptahydrate crystals are gently heated, it loses
seven water molecules, and becomes anhydrous magnesium sulphate
b) Solubility is defined as the number of grams of a solute that can be dissolved in 100g
of a solvent to form its saturated solution at a given temperature and pressure.
Solubility = x 100
M ass of the solute
M ass of the solvent
85) Explain Solid solution, Liquid solution and Gaseous solution.

Answer :
SoluteSolventExample
Solid solution
Solid Solid Copper dissolved in gold (Alloys)
Liquid Solid Mercury with sodium (amalgam)
Liquid solution
Solid Liquid Sodium chloride dissolved in water
Liquid Liquid Ethyl alcohol dissolved in water
Gas Liquid carbon-di-oxide dissolved in water (Soda water)
Gaseous solution
Liquid Gas Water vapour in air (cloud)
Gas Gas Mixture of Helium-Oxygen gases,
86) What are called thermolysis reactions?
Answer : In this type of reaction, the reactant is decomposed by applying heat. As the
molecule is dissociated by absorption of heat, it is otherwise called 'Thermolysis:
87) Explain the types of double displacement reactions with examples.

Answer : There are two major classes of double displacement reactions. They are
(i) Precipitation Reactions
(ii) Neutralization Reactions
(i) Precipitation Reactions : When aqueous solutions of two compounds are mixed, if they
react to form an insoluble compound and a soluble compound, then it is called
precipitation reaction
Pb(NO3)2(aq)+ 2KI(aq) ⟶ PbI2(S) + 2KNO3(aq)
(ii) Neutralization Reactions : Acid reacts .s with the base to form a salt and water. It is t
called neutralization reaction as both acid tI and base neutralise each other.
Acid + Base ⟶ Salt + Water
HCI(aq)+ NaOH(aq) ⟶NaCI(aq)+ H2O(I)
88) Explain the classification based on the direction of the reaction.
Answer : Reversible Reactions: A reversible reaction is a reaction that can be reversed,
i.e., the products can be converted back to the reactants. A reversible reaction is
represented by a double arrow with their heads in the direction opposite to each other.
Thus, a reversible reaction can be rept
Explanation: The compound 'AB' undergoes decomposition to form the products 'A' and
'B'.It is the forward reaction. As soon as the products are formed, they combine together
to form 'AB': It is the backward reaction
PCl5(g) ⇌ PCl3(g) +CI2(g)
Irreversible Reactions : The reaction that cannot be reversed is called irreversible
reaction. Consider the combustion of coal into carbon dioxide and water.
C(s) +O2(g) ⟶ CO2(g)+Heat
Coal oxygen Carbon dioxide
In this reaction, solid coal burns with oxygen and gets converted into carbon dioxide gas
and water. As the product is a gas, as soon as it is formed it escapes out of the reaction
container. It is hard to decompose a gas into a solid. Thus, the backward reaction is not
possible in this case. So, it is an irreversible reaction
89) What is called homologous series? Give any three of its characteristics?
Answer : Homologus series is a group or a class of organic compounds having same
general formula & similar chemical properties in which the successivenumbers differ by a
-CH2 group.
Characteristics of homologous series :
(i) Each member of the series differs from the preceding or succeeding member by one
methylene group (-CH2) and hence by a molecular mass of 14 amu.
(ii) All members of a homologous series contain the same elements and functional group.
(iii) Theyare represented by a general molecular formula. e.g. Alkanes, CnH2n + 2
(iv) The members in each homologous series show a regular gradation in their physical
properties with respect to their increase in molecular mass.
(v) Chemical properties of the members of a homologous series are similar.
(vi) All the members can be prepared by a common method.
90) Arrive at, systematically, the IUPAC name of the compound: CH3–CH2–CH2–OH.
Answer : Stept: The parent chain consists of 3 carbon atoms. The root word is 'Prop'.
Step 2: There are single bonds between the carbon atoms of the chain. So, the primary
suffix is 'ane'
Step 3: Since, the compound contains - OH group, it is an alcohoL The carbon chain is
numbered from the end which is closest to -OH group. (Rule 3)
Step 4: The locant number of -OH group is 1 and thus the secondary suffix is '1-ol'
The name of the compound is Prop + ane + (1-ol) = Propan-l-ol Note:Terminal 'e'of'ane' is
removed as per Rule5
91) How is ethanol manufactured from sugarcane?
Answer : Ethonol Manufacture: Ethanol ismanufactured in industries by the
fermentation of molasses, which is a by-product obtained during the manufacture of
sugar from sugarcane. Molasses is a dark coloured syrupy liquid left after the
crystallization of sugar from the concentrated sugarcane juice. Molasses contain about
30% of sucrose, which cannot be separated by crystallization. It is converted into ethanol
by th following steps:
(i) Dilution of molasses : Molasses is first ts diluted with water to bring down the U
concentration of sugar to about 8 to 10%.
(ii) Addition of Nitrogen source : Molasses usually contains enough nitrogenous matter to
act as food for yeast during the fermentation process. If the nitrogen content of the
molasses is poor, it may be fortified by the addition of ammonium sulphate or ammonium
phosphate.
(iii) Addition of Yeast: The solution obtained in step (ii) is collected in large 'fermentation
tanks' and yeast is added to it. The mixture is kept at about 303K for a few days. During
this period, the enzymes invertase and zymase present in yeast, bring about the
conversion of sucrose into ethanol
The fermented liquid is technically called wash.

(i.e. wash), containing 15 to 18 percent alcohol, is now subjected to fractional distillation.
The main fraction drawn is an aqueous solution of ethanol which 'contain 95.5% of
ethanol and 4.5% of water. This is called rectified spirit. This mixture is then refluxed
over quicklime for about 5 to 6 hours and then allowed to stand for 12 hours. On
distillation of this mixture, pure alcohol (100%) is obtained. This is called absolute
alcohol.
92) Write the characteristics of organic compounds.
Answer : (i) Organic compounds have high molecular weight and complex structure
(ii) They are mostly insoluble in water and soluble in organic solvents such as ether,
carbon tetrachloride, toluene, etc.
(iii) They are highly flammable.
(iv) Organic compounds are less reactive compared to inorganic compounds.
(v) Organic compounds form covalent bonds.
(vi) They have lower melting point and boiling point.
(vii) They exhibit the phenomenon ofisomerism.
(viii) They are volatile in nature.
(ix) They can be prepared in the laboratory.
93) How will you classify organic compounds based on the pattern of carbon chain?
Answer : Organic compounds are classified into two types as follows:
(i) Acyclic or Open chain compounds:
These are the compounds in which the carbon atoms are linked in a linear pattern to
form the chain. If all the carbon atoms in the chain are connected by single bonds, then
the compound is called as saturated. If one or more double bonds or triple bonds exist
between the carbon atoms, then the compound is said to unsaturated.
(ii) Cyclic Compounds:

Organic compounds in which the chain of carbon atoms is closed or cyclic are called
Cyclic compounds. If the chain contains only carbon atoms, such compounds are called
carbocyclic compounds. If the chain contains carbon and other atoms like oxygen,
nitrogen, sulphur, etc., these compounds are called heterocyclic compounds. Carbocyclic
compounds are further subdivided into alicyclic and aromatic compounds. In alicyclic
compounds, the carbon cycle contains only single bonds whereas aromatic compounds
contain one or more benzene rings (ring containing alternate double bonds between
carbon atoms).
E.g:
94) How will you classify hydrocarbonsf

Answer : Hydrocarbons are classified into three classes such as:
(i) Alkanes
(ii) Alkenes
(iii) Alkynes
(i) Alkanes: These are hydrocarbons which contain only single bonds. They are
represented by the general formula CnH2n + 2 (where n = 1,2,3, ).
Ex: Methane (CH4).
(ii) Alkenes: The hydrocarbons which contain one or more C=C bonds are called alkenes.
These are unsaturated compounds. They are represented by the general formula CnH2n.
(iii) Alkynes: The hydrocarbons containing carbon to carbon triple bond are called
alkynes. They have the general formula CnH2n-2.
Ex : Acetylene (C2H2)
95) Write the characteristics of hydrocarbons.
Answer : Characteristics of hydrocarbons
(i) Lower hydrocarbons are gases at room temperature
(ii) Alkanes are least reactive where Alkynes are most reactive due to presence triple bond
(iiI) Alkanes are saturated whereas alkenes and alkynes are unsaturated
(iv) They are insoluble in water
Part - D 5 x 7 = 35
96) 1.Calcium carbonate is decomposed on heating in the following reaction
CaCO3 → CaO + CO2
i. How many moles of Calcium carbonate are involved in this reaction?
ii. Calculate the gram molecular mass of calcium carbonate involved in this reaction
iii. How many moles of CO2 are there in this equation?
Answer : CaCO3 ➝ 7 CaO + CO2
(i) No of moles of CaCO3
involved in this reaction = 1
(ii) Molar mass of calcium = 40
Molar mass of carbon = 12
Molar mass of oxygen = 16
Gram molecular mass of CaCO3 = Molar mass of calcium + Molar mass of carbon + Molar
mass of oxygen x 3
= 40 + 12 + (16 x 3)
= 100 g / mol.
(iii) No of moles of CO2 in the reaction = 1
97) Name the acid that renders aluminium passive. Why?
Answer : Dilute or concentrated nitric, acid does not attack aluminium, but it renders
aluminium
passive due to the formation of an oxide film on its surface.
98) 'A' is a blue coloured crystaline salt. On heating it loses blue colour and to give 'B'. When
water is added, 'B' gives back to 'A'. Identify A and B, write the equation
Answer :
99) A solid compound ‘A’ decomposes on heating into ‘B’ and a gas ‘C’. On passing the gas
‘C’ through water, it becomes acidic. Identify A, B and C.
Answer :
A CaCo3 Calcium carbonate

BCaO Calcium oxide
CCO2 Carbon di oxide
100) An organic compound ‘A’ is widely used as a preservative and has the molecular
formula C2H4O2. This compound reacts with ethanol to form a sweet smelling compound
‘B’.
(i) Identify the compound ‘A’.
(ii) Write the chemical equation for its reaction with ethanol to form compound ‘B’.
(iii) Name the process.
Answer : (i) Ethanoic acid (acetic acid).
(ii) CH3COOC2H5 (Ethyl acetate).
(iii) Esterification
7 Marks Problems 4 x 7 = 28
101) Calculation of molar mass
Calculate the gram molar mass of the following.
1) H2O
2) CO2
3) Ca3 (PO4)2
Answer : 1) H2O
Atomic masses of H = 1, O = 16
Gram molar mass of H2O
= (1 × 2) + (16 × 1)
= 2 + 16
Gram molar mass of H2O = 18g
2)CO2
Atomic masses of C = 12, O = 16
Gram molar mass of CO2
= (12 × 1) + (16 × 2)
= 12 + 32
Gram molar mass of CO2 = 44 g
3) Ca3 (PO4)2
Atomic masses of Ca = 40, P = 30, O = 16.
Gram molar mass of Ca3 (PO4)2
= (40 × 3) + [30 + (16 × 4)] × 2
= 120 + (94 × 2)
= 120 + 188
Gram molar mass of Ca3(PO4)2 = 308 g
102) Find the gram molecular mass of carbon dioxide (CO2)
Answer : CO2 = 1(C) + 2(O) = 1(12) + 2(16) = 12 + 32 = 44
Gram molecular mass of CO2 = 44g.
103) 1.5 g of solute is dissolved in 15 g of water to form a saturated solution at 298K. Find
out the solubility of the solute at the temperature.
Answer : Mass of the solute = 1.5 g
Mass of the solvent = 15 g
Solubility of the solute = M ass of
X 100
the solute
M ass of the solvent
Solubility of the solute = 1.5

X 100
15
= 10 g
104) Calculate the pH of 0.001 molar solution of HCl.
Answer : HCl is a strong acid and is completely dissociated in its solutions according to
the process:
HCl(aq) → H+(aq) + Cl–(aq)
From this process it is clear that one mole of HCl would give one mole of H+ ions.
Therefore, the concentration of H+ ions would be equal to that of HCl, i.e., 0.001 molar or
1.0 × 10–3 mol litre–1
Thus, [H+] = 1 × 10-3mol litre–1.
pH = –log10[H+] = –log1010–3
= –(–3 × log ) = –(3 × 1) = 3
10
Thus, pH = 3

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10th Study materials

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Zeal centum Study SSLC only

4Al + 3O2 ⟶ 2Al2 O 3 (B)

(ii) Benzene Cyclic Aromatic Compound

(iv) Furan Hele Trocyclic

73) What are hydrocarbons?

75) What is rectified spirit??

85) Explain Solid solution, Liquid solution and Gaseous solution.

87) Explain the types of double displacement reactions with examples.

The fermented liquid is technically called wash.

(ii) Cyclic Compounds:

94) How will you classify hydrocarbonsf

A CaCo3 Calcium carbonate

M ass of the solvent

Solubility of the solute = 1.5

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