Question

2.8 g of calcium oxide ($CaO$) prepared by heating limestone was found to contain 0.8 g of oxygen. When one gram of oxygen was treated with calcium, 3.5 g of calcium oxide was obtained. Show that the results illustrate the law of definite proportions.

Answer 1

Law of definite proportion states that a given compound always contains exactly the same proportion of elements by weight.

$\underset{–}{\text{Case 1:}}$ $Ca2.8g$ $O0.8g$ $⟹1g$ of $O$ reacts with $=\frac{2.8}{0.8}=3.5g$ of $CaO$

$\underset{–}{\text{Case 2:}}$ $3.5g$ $1g⟹1g$ of $O$ reacts qith $3.5g$ of $CaO.$

Ratio of $O$ reacting with $Ca$ to form $CaO$ is $1:1$.

Hence results illustrate the law of definite proportion.