Question

Solve problem:

2.0 g of a metal burnt in oxygen gave 3.2 g of its oxide. 1.42 g of the same metal heated in steam gave 2.27 of its oxide. Which law is verified by these data?

Answer 1

Here, the metal oxide is obtained by two different methods; reactions of metal with oxygen and reaction of metal with water vapor (steam).
In the first reaction (reaction with oxygen),
The mass of oxygen in metal oxide = 3.2 − 2.0 = 1.2 g
% of oxygen = `1.2/3.2xx100` = 37.5%
% of metal = `2.0/3.2xx100` = 62.5%
In second reaction (reaction with steam),
The mass of oxygen in metal oxide = 2.27 − 1.42 = 0.85 g
% of oxygen = `0.85/2.27xx100` = 37.44 ≈ 37.5%
% of metal = `1.42/2.27xx100` = 62.56 ≈ 62.5%
Therefore, irrespective of the source, the given compound contains same elements in the same proportion. The law of definite proportions states that “A given compound always contains exactly the same proportion of elements by weight”. Hence, the law of definite proportions is verified by these data.
The law of definite proportions is verified by the given data.