{b} In experiment B. the iron filings weighed 2.0g at the beginning of the experiment
and the iron sulphide produced weighed 2.8g.
Explain this increase in mass.

Explanation:

The increase in mass is because the iron fillings have combined with a sulfide to produce iron sulfide and so the mass will increase.

In such a reaction like this, the mass of the reactants must be conserved. By so doing, the mass of reactants and products must be the same.

When two substances combine together, their masses added up to that of the individual masses. This helps to conserve the mass.

answer; /// i do believe that the correct answer is (a) boiling

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%