5. Given that a 40.14 g sample of hydrated NiSO4•XH2O is reduced in mass to 2.14 g upon heating.

Determine the value of X.

Value of X is 7

Explanation:

We are given;

Mass of the Hydrated sample as 40.14 g Mass of the anhydrous salt as 22.14 g (Missing in the question)

We are required to determine the value of X in the hydrated sample, NiSO4•XH2O.

First, we determine the mass of the anhydrous salt Mass of water of crystallization = Mass hydrate sample - Mass of anhydrous sample

= 40.14 g - 22.14 g

= 18.0 g

We can determine the value of X by determine simple number ratio of anhydrous compound and water molecules.

Determine the number of moles Molar mass of NiSO₄ = 154.75 g/mol Moles of NiSO₄ = 22.14 g : 154.75 g/mol

= 0.1431 mole

Molar mass of water = 18.02 g/mol

Moles of water = 18.0 g : 18.02 g/mol

= 1.00 mole

We can then determine the mole ratio.

Mole ratio = 0.1431 mole : 1.00 mole

= 0.1431 mole/0.1431 mole : 1.00 mole/0.1421 mole

= 1 : 7.03

= 1 : 7

Therefore, the formula of the hydrated salt is NiSO₄•7H₂O

Thus, the value of X is 7