Chemistry Class-11: Chapter –1. Some Basic Concepts of Chemistry – Part-2

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Questions-9

What is the mass percent of carbon in carbon dioxide?

(i)

(ii)

(iii)

(iv)

Answer: (ii)

Questions-10

The empirical formula and molecular mass of a compound are and respectively. What will be the molecular formula of the compound?

(i)

(ii)

(iii)

(iv)

Answer: (iii)

Questions-11

If the density of a solution is , the mass of solution in significant figures is _______.

(i)

(ii)

(iii)

(iv)

Answer: (i)

Questions-12

Which of the following statements about a compound is incorrect?

(i) A molecule of a compound has atoms of different elements.

(ii) A compound cannot be separated into its constituent elements by physical methods of separation.

(iii) A compound retains the physical properties of its constituent elements.

(iv) The ratio of atoms of different elements in a compound is fixed.

Answer: (iii)

Questions-13

Which of the following statements is correct about the reaction given below:

(i) Total mass of iron and oxygen in reactants total mass of iron and oxygen in product therefore it follows law of conservation of mass.

(ii) Total mass of reactants total mass of product; therefore, law of multiple proportions is followed.

(iii) Amount of can be increased by taking any one of the reactants (iron or oxygen) in excess.

(iv) Amount of produced will decrease if the amount of any one of the reactants (iron or oxygen) is taken in excess.

Answer: (i)

Questions-14

Which of the following reactions is not correct according to the law of conservation of mass.

(i) 2Mg(s) + O2(g) ⎯→ 2MgO(s)

(ii) C3H8(g) + O2(g) ⎯→ CO2(g) + H2O(g)

(iii) P4(s) + 5O2(g) ⎯→ P4O10(s)

(iv) CH4(g) + 2O2(g) ⎯→ CO2(g) + 2H2O (g)

Answer: (ii)

Questions-15

Which of the following statements indicates that law of multiple proportion is being followed.

(i) Sample of carbon dioxide taken from any source will always have carbon and oxygen in the ratio 1:2.

(ii) Carbon forms two oxides namely and , where masses of oxygen which combine with fixed mass of carbon are in the simple ratio 2:1.

(iii) When magnesium burns in oxygen, the amount of magnesium taken for the reaction is equal to the amount of magnesium in magnesium oxide formed.

(iv) At constant temperature and pressure of hydrogen will combine with oxygen to produce of water vapour.

Answer: (ii)