Chemistry Class 11 NCERT Solutions: Chapter 1 Some Basic Concepts of Chemistry Part 3

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Q: 7. How Much copper can be obtained from 100 g of copper sulphate ?

Answer: contains 1 mole of copper.

Molar mass of

contains of copper.

∴Amount of copper that can be obtained from

Q: 8 Determine the molecular formula of an oxide of iron in which the mass per cent of iron and oxygen are 69.9 and 30.1 respectively. Given that the molar mass of the oxide is

Answer: Mass percent of iron

Mass percent of oxygen

Number of moles of iron present in the oxide

Number of moles of oxygen present in the oxide

Ratio of iron to oxygen in the oxide,

∴ The empirical formula of the oxide is

Empirical formula mass of

Molar mass of

Molecular formula of a compound is obtained by multiplying the empirical formula with n. Thus, the empirical formula of the given oxide is

Hence, the molecular formula of the oxide is

Q: 9 Calculate the atomic mass (average) of chlorine using the following data:

Abundance and molar mass of Cl isotopes

% Natural Abundance

Molar Mass



Answer: The average atomic mass of chlorine

∴ The average atomic mass of chlorine