Question

6.488g of lead combine directly with 1.002g of oxygen to form lead peroxide .lead peroxide is also produced by heating lead nitrate and it was found that the percentage of oxygen present in lead peroxide is 13.38%.Use this data to illustrate law of constant composition

Answer 1

In the first reaction,

Pb + O₂ ---------> PbO₂
6.488g Pb combines with 1.002g of O₂
so, mass of PbO₂ formed=(6.488+1.002)g
=7.490g
7.490g of lead peroxide combines with 1.002g of oxygen
Therefore, percentage of oxygen = $\frac{1.002}{7.490}\times 100$

= 13.38%
In second reaction also, the percentage of oxygen present in PbO₂ will be 13.38% which is alredy given.
Since, the percentage composition of oxygen in both reactions will be identical. Hence, the above data illustrates the law of constant proportion.