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

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Q: 1 Calculate the molecular mass of the following:

Example of molecular mass for carbon dioxide

Structure of Molecular Mass

Example of molecular mass for carbon dioxide

(i)

Molecular Atomic mass of 2 hydrogen + 1 oxygen

Structure of Molecular Mass of H2O

Molecular Atomic mass of 2 hydrogen + 1 oxygen

(ii)

Molecular Atomic mass of 1 carbon +2 oxygen

Structure of Molecular Mass of CO2

Molecular Atomic mass of 1 carbon +2 oxygen

(iii)

Molecular Atomic mass of 1 carbon + 4 hydrogen

Structure of Molecular Mass CH4

Molecular Atomic mass of 1 carbon + 4 hydrogen

Answer:

(i)

The molecular mass of water,

(ii)

The molecular mass of carbon dioxide,

(iii)

The molecular mass of methane,

=

Q: 2 calculate the mass percent of different elements present in sodium sulphate

Na2SO4 is a typical ionic sulfate, containing Na+ ions and SO42- ions

Structure of Sodium Sulphate Na2SO4

Na2SO4 is a typical ionic sulfate, containing Na+ ions and SO42- ions

Answer:

The molecular formula of sodium sulphate is

Molar mass of

Mass percent of an element

∴ Mass percent of sodium:

Mass percent of sulphur:

Mass percent of oxygen:

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