1.375gof cupric oxide was reduced by heating in a current of hydrogen and the weight of copper that remained was 1.098 g. In another experiment, 1.179 g of copper was dissolved in the nitric acid and the resulting copper nitrate was converted into cupric oxide by ignition. The weight of cupric oxide formed was 1.476 g. Show that these results illustrate the law of constant composition.
In the first experiment,
Cuo + ${ H }_{ 2 }$ -------------> Cu +
${ H }_{ 2 }O$
Since 1.375 g CuO is reduced to 1.098 g Cu, hence, the mass of oxygen is 1.375 - 1.098 = 0.277 g.
Thus, the percentage of Cu= 1098 / 1.375 x 100 = 79.85%
In the second experiment, mass of CuO = 1.476 g
Mass of Cu = 1.179 g
Mass of oxygen = 1.476 - 1.179 = 0.297 g
Thus, the percentage of Cu = 1.179 / 1.476 x 100 = 79.87%
Since % of Cu is same in both the experiments, hence the law of constant composition is proved.