Question

A hydrated salt Na2CO3.nH2O retained its 37% mass on heating. What is number of the water of crystallization?

Answer 1

Given:

The mass retained on heating = 37 %

To Find:

The number of the water of crystallization present in the salt.

Calculation:

- The molar mass of salt:

W = (106 + 18 n) gm  .....(i)

- Let us take (106 + 18 n) gm of the salt.

- On heating, we get:

(37/100) × W = 106

⇒ W = 10600/37 = 286.49 gm

- Putting in eqn (i), we get:

286.49 = (106 + 18 n)

⇒ n = (286.49 - 106)/ 18

⇒ n = 180.49/18

⇒ n = 10.027 ≈ 10

- So, the number of the water of crystallization present in the salt is Ten (10).