Question

30g of nitric oxide were passed slowly over heated copper , if the increase in weight of copper is 10g calculate weight of NO remaining undecomposed​

Answer 1

First experiment

∙ Copper oxide =1.375g

∙ Copper left =1.098g

∙ Oxygen present =1.375−1.098=0.277g

Percentage of oxygen in CuO=(0.277)(100 %) 1.375=20.15 %

Second Experiment

∙ Copper taken =1.179g

∙ Copper oxide formed =1.476g

∙ Oxygen present =1.476−1.179=0.297g

Percentage of oxygen in CuO=(0.297)(100 %) 1.476=20.12 %

Percentage of oxygen is approximately (within significant figures limit) the same in both the above cases. So the law of constant composition is illustrated.

In chemistry, the law of definite proportion, sometimes called Proust's law or the law of definite composition, or law of constant composition states that a given chemical compound always contains its component elements in fixed ratio and does not depend on its source and method of preparation.