Question

The equivalent mass of an element is 3. The vapour density of its volatile chloride is 77. The atomic weight of that element is:

• A. 3
• B. 6
• C. 9
• D. 12

Answer 1

The correct option is D 12

Vapour density $=$ $\frac{1}{2}$ Molecular weight

Therefore, molecular mass of the chloride $=$ $77\times 2$ $=$ $154$.

Also, molecular mass of the chloride $=3\times x+x\times 35.5$ ( where $x$ is the valency of the element).

On solving, we get $x$ $=$$4$.

Therefore, atomic mass $=$ $4\times 3$ $=$ $12$.