# Chemistry Class 11 NCERT Solutions: Chapter 1 Some Basic Concepts of Chemistry Part 2

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Q: 3 Determine the empirical formula of an oxide of iron which has 69.9% iron and 30.1% Dioxygen by mass.

% of iron by mass = 69.9 % [Given]

% of oxygen by mass = 30.1 % [Given]

Relative moles of iron in iron oxide:

Relative moles of oxygen in iron oxide:

Simplest molar ratio of iron to oxygen:

Q: 4 calculate the amount of carbon dioxide that could be produced when

(i) 1 mole of carbon is burnt in air.

(ii) 1 mole of carbon is burnt in 16 g of Dioxygen.

(iii) 2 moles of carbon are burnt in 16 g of Dioxygen

The balanced reaction of combustion of carbon can be written as:

(i) As per the balanced equation, 1 mole of carbon burns in 1 mole of Dioxygen (air) to produce 1 mole of carbon dioxide.

(ii) According to the question, only 16 g of Dioxygen is available. Hence, it will react with mole of carbon to give 22 g of carbon dioxide. Hence, it is a limiting reactant.

(iii) According to the question, only 16 g of Dioxygen is available. It is a limiting reactant. Thus, 16 g of Dioxygen can combine with only 0.5 mole of carbon to give 22 g of carbon dioxide.

Q: 5. Calculate the mass of sodium acetate required to make 500 mL of 0.375 molar aqueous solutions. Molar mass of sodium acetate is

0.375 M aqueous solution of sodium acetate

mL of solution containing 0.375 moles of sodium acetate

∴Number of moles of sodium acetate in 500 mL

mole

Molar mass of sodium acetate

Q: 6 Calculate the concentration of nitric acid in moles per litre in a sample which has a density, and the mass per cent of nitric acid in it being

Mass percent of nitric acid in the sample

Thus, 100 of nitric acid contains of nitric acid by mass.

Molar mass of nitric acid