0.79 g of iron unite directly with 0.4 g sulphur to form ferrous sulphate. If 2.8 g of iron are dissolved in dilute HCl and excess of sodium sulphide solution is added, 4.4 g iron sulphite is precipitated. Show that the data is according to Law of constant composition.

Explanation

In the first sample :
Ratio by mass of iron and sulphur is : 0.7 : 0.4 or 7 : 4
In the second sample
Mass of iron dissolved = 2.8 g
Mass of iron sulphide formed = 4.4 g
Mass of sulphuric reacted `= (4.4 - 2.8) = 1.6 g`
Ratio of mass of iron and sulphur is : 2.8 : 1.6 or 7 : 4
Since the ratio by mass of Fe and S in the two samples is the same, this verifies the Law of constant composition.