Question

Which of the folIowing pair of compounds illustrate the law of multiple proportions?

• A. $S{O}_2$ and $S{O}_3$
• B. $N{O}_2$ and $N_{2}O$
• C. $MgO$ and $Mg(OH{)}_2$
• D. $NO$ and $N_2{O}_5$

Answer 1

Answer: (A), (B), (D)

$S{O}_2$ and $S{O}_3$
$N{O}_2$ and $N_{2}O$
$NO$ and $N_2{O}_5$

The following pairs of compounds illustrate the law of multiple proportions:
$S{O}_2$ and $S{O}_3$
$N{O}_2$ and $N_{2}O$
$NO$ and $N_2{O}_5$
According to the law of multiple proportions, if two elements chemically combine with each other forming two or more compounds, with different compositions by mass then the ratios of masses of two interacting elements in the two compounds are small whole numbers.
Consider the example $S{O}_2$ and $S{O}_3$
For $S{O}_2$ $\frac{\text{32 g oxygen}}{\text{32 g sulphur}}=\text{1}$
For $S{O}_3$ $\frac{\text{48 g oxygen}}{\text{32 g sulphur}}=\text{1.5}$
The two ratios are in proportion $\frac{1}{1.5}=2:3$