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

This Structure is sodium hydroxide and copper sulfate and Solid copper hydroxide in colouriess sodium sulfate solution.

Structure of Sodium Sulphate

This Structure is sodium hydroxide and copper sulfate and Solid copper hydroxide in colouriess sodium sulfate solution.

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: