Question

g Copper (II) Sulfate forms several hydrates with the general formula CuSO4 times xH2O, where x is an integer. If the hydrate is heated, the water can be drive off leaving pure CuSO4 behind. Suppose a sample of a certain hydrate is heated until all water is removed, and its found that the mass of the sample decreases by 31%. Which hydrate is it? THat is, WHAT IS X?

Answer 1

Answer:

Water of crystallization, X = 4.

Explanation:

Molar mass of $CuSO_{4}.XH_{2} O$

64 + 32 + (4x18) + x ( 1 × 2 + 16)

= 160 + 18x

Given: % water of crystallization (decrease in mass after heating) = 30%

⇒ $\frac{18x}{160 + 18x} =\frac{31}{100}$

1800x = 31 (160 + 18x)

58.0645x = 160 + 18x

(58.0645 - 18)x = 160

x = $\frac{160}{40.0645}$ = 3.99 ≅ 4.

Water of crystallization, X = 4.