Question

Two different oxides of a metal contain 20% and 27% oxygen by weight. This is in accordance with the law of:

• A. Conservation of mass
• B. Constant composition
• C. Multiple proportions
• D. Reciprocal proportions

Answer 1

The correct option is C Multiple proportions

In the first compound, the mass of oxygen is $20\text{g}$ and the mass of the metal will be $100-20=80\text{g}$
Therefore, the mass of oxygen that combines with $1\text{g}$ of metal $=\frac{20}{80}=0.25\text{g}$
In the second compound, the mass of oxygen is $27\text{g}$ and the mass of the metal will be $100-27=73\text{g}$
Therefore, the mass of oxygen that combines with $1\text{g}$ of metal $=\frac{27}{73}=0.37\text{g}$
Thus, the ratio of oxygen combining with a fixed mass of metal is $0.25:0.37$ or $1:1.5$ Or $2:3$ which is a simple ratio.
It proves the law of multiple proportions which states that when two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.