Question

$158.5\, g$ of chloride occupies a volume of $22.4 \,L$ at STP. The percentage of chlorine in this chloride is $44.71 \%$. The atomic weight and valency of the element is

• A. 88,2
• B. 88,1
• C. 71,2
• D. 71,1

Answer 1

Answer: (A)

Molecular weight of chloride $=158.5$

Let the formula of chloride is $M Cl _{x}$.

Let the equivalent weight of metal $M$ is $Y$.

Then, molecular weight of $M Cl _{x}=y \times x+x \times 35.5=158.5$

Equivalent weight of an element is the weight that combines with $35.5\, g$ of chlorine.

Equivalent weight of $M=\frac{55.29}{44.71} \times 35.5=44$

$44 \times x+35.5 \times x=158.5$

$ \Rightarrow x=2$

Atomic weight of element, $M=44 \times 2=88$

Valency $=2$

Alternatively, amount of chlorine in chloride

$=158.5 \times \frac{44.71}{100}=70.8 \,g $

i.e, $ \frac{70.8}{35.5} \approx 2 \,mol$

$\therefore $ Atomic weight of element $M=158.5-70.8$

$=87.6 \approx 88$

Formula is $M Cl _{2}$, valency $=2$