Question

In an experiment, 1.288 g of copper oxide was obtained from 1.03 g of copper. In another experiment, 3.672 g of copper oxide gave, on reduction, 2.938 g of copper. Show that these figures verify the law of constant proportions.

Answer 1

(a) In the first experiment:

Weight of copper oxide, $\left(CuO\right)=1.288g$

Weight of copper $=1.03g$

Weight of oxygen $=$ Wt. of copper oxide $-$ Wt. of copper $=1.288-1.03=0.258g$

$\therefore \frac{\text{Wt. of copper}}{\text{Wt. of oxygen}}=\frac{1.03}{0.258}\approx \frac{4}{1}$

(b) In the second experiment:

Weight of copper oxide $\left(CuO\right)=3.672g$

Weight of copper $=2.938g$

Weight of oxygen $=$ Wt. of copper oxide $-$ Wt. of copper $=3.672-2.938=0.734g$

$\therefore \frac{\text{Wt. of copper}}{\text{Wt. of oxygen}}=\frac{2.938}{0.734}\approx \frac{4}{1}$

The proportion of weights of copper and oxygen in both experiments is same.

Hence, law of constant proportion is proved.