Question

The chloride of a solid metallic element contains 57.89% by mass of the element. The specific heat of the element is $0.0324calde{g}^{-1}{g}^{-1}$. Calculate the exact atomic mass of the clement.

• A. 195.2
• B. 195
• C. 195.9
• D. 194

Answer 1

The correct option is A 195.2

% of element is given in this question = 57.89

so % of chlorine is = 100-57.89 = 42.11

Equivalent wt of metal= $\frac{57.89}{42.11}\times 35.5$ = 48.8

specific heat of metal= 0.0324

$\to$ According to Dulong and Petit's law

Approx atomic wt of metal= $\frac{6.4}{specificheat}=\frac{6.4}{0.0324}$ = 197.53

Valency of metal= Approximate atomic wt/ Equivalent wt

= $\frac{197.53}{48.8}$ = 4.04 = 4

Exact atomic wt of metal = $Equivalentwtofmetal\times Valencyofmetal$ = 48.8 x 4

= 195.2

answer is A