Question

The sulphate of a metal $M$ contains $9.87\%$ of $M$. This sulphate is isomorphous with $ZnS{O}_4.7H_{2}O$. The atomic weight of $M$ is:

• A. $40.3$
• B. $36.3$
• C. $24.3$
• D. $9.87$

Answer 1

The correct option is D $9.87$

1) Consider the molecular weight of the metal be M

Now as it is isomorphous with $ZnS{O}_4.7H_{2}O$ it would be of the formula $MS{O}_4.7H_{2}O$

Percentage of M in the compound would be

$M\times \frac{100}{M}+$ weight of $S{O}_4+7\times$ weight of $H_{2}O$

$=\frac{M\times 100}{M+96+126}$

$=9.87$