Question

What is present in a sample of pure water irrespective of the source?

Answer 1

Sample of Pure water $({\mathrm{H}}_2\mathrm{O})$

• When a sample of pure water is taken from the source it contains 88.8% by mass of oxygen and 11.1% by mass of hydrogen.
• The pure water $({\mathrm{H}}_2\mathrm{O})$ molecule consists of two hydrogen atoms of relative mass 1 and one oxygen atom of relative mass 16.

Explanation :

• According to the law of constant composition in a given compound, a chemical compound always contains exactly the same proportion of elements by mass irrespective of the source from which it is obtained.
• Therefore, the ratio in which $2$ atoms of hydrogen and one atom of oxygen are combined is $2:16$ or in the simplest ratio $1:8$ and this will always be the same irrespective of the source of water.