Chemical reaction is the final part of the sentence

b) 3A  + 2B   →   C

Explanation:

In given ratios of substances there are three mole of reactant A two moles of reactant B and one mole of product C are present.

A : B     3 : 2                          A : C     3 :  1             B : C        2  :  1

So from given information option b is correct.

3A  + 2B   →   C

Here in this equation three moles of A , two moles of B and one mole of C are present.

Other options are incorrect because,

a) 6A  + 6B   →   2C

In this chemical equation six moles of A six moles of B and two mole of C are present. So it is incorrect.

c) A + 2B →   3C

In this chemical equation one mole of A two mole of B and three moles of C are present. So it is incorrect.

d) A + B →   C

In this chemical equation one mole of A one mole of B and one mole of C are present. So it is incorrect.

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%