Question

Irrespective of the source, a pure sample of water always yields 88.29% mass of oxygen and 11.11% mass of hydrogen. This is explained by the law of:
A. Conservation of mass
B. Constant proportion
C. Multiple proportion
D. Constant volume

Answer 1

Hint: The law of constant proportion is also known as the law of constant composition. It was discovered by Joseph Proust. Any pure sample of a compound, no matter the source, will always consist of the same elements that are present in the same ratio by mass.

Complete step by step answer:
The law states that a chemical compound always contains the same elements combined together in the same proportion by mass. Hence, irrespective of its sources, a pure compound contains the same elements in the same proportion. Thereby, a pure sample of water always yields 88.89% mass of oxygen and 11.11% mass of hydrogen as oxygen makes up \[\dfrac{8}{9}th\]pf the mass of water.
$ \Rightarrow $As we know, the molecule of water consists of two hydrogen atoms and one hydrogen atom.
$ \Rightarrow $${H_2}O \to $ mass of compound = (mass of hydrogen) x $2$+ (mass of oxygen)
$ \Rightarrow $\[\left( {1{\text{ }}x{\text{ }}2} \right){\text{ }} + {\text{ }}\left( {16} \right){\text{ }} + {\text{ }}2{\text{ }} + {\text{ }}16{\text{ }} = {\text{ }}18\]
$ \Rightarrow $mass of oxygen = $\dfrac{{16}}{{18}} = \dfrac{8}{9}$
$ \Rightarrow $mass of hydrogen = $\dfrac{2}{{18}} = \dfrac{1}{9}$
$ \Rightarrow $Thus, option B is the right answer.
Irrespective of the source, a pure sample of water always yields 88.29% mass of oxygen and 11.11% mass of hydrogen. This is explained by the law of: constant proportion

Note:
The experiment was verified after performing a few experiments such as respiration, burning of coal, by heating limestone, sodium bicarbonate, by the reaction of dilute hydrochloric acid, and calcium carbonate. All these produce carbon dioxide. There are few exceptions, one such example is wustite, an oxide of iron with the chemical formula FeO. The ratio of iron and oxygen atoms can range from 0.83:1 to 0.95:1. Since natural polymers can vary in their compositions, various samples can show different mass proportions.