Question

$0.701 \,g$ of silver salt of a dibasic acid on ignition yielded $0.497 \,g$ of metallic silver. Molecular weight of the acid is $( Ag =108)$

• A. 90.7
• B. 304.7
• C. 88.7
• D. 197.7

Answer 1

Answer: (A)

$H_{2}A \to \underset{0.701}{Ag_{2}A} \to \underset{0.497}{2Ag}$

Molecular weight of silver salt $=\frac{0.10}{0.497} \times 2 \times 108=304.7$

Molecular weight of acid $=304.7-2 \times$ atomic mass of silver $+$ $2 \times$ atomic mass of hydrogen $=304.7-2 \times 108+2 \times 1=90.7$ Alternatively,

Equivalent mass of acid $=\frac{108 \times \text { Mass of silver salt }}{\text { Mass of Ag metal }}-107$

Equivalent mass of acid $=\frac{108 \times 0.701}{0.497}-107=45.33$

Molecular mass $=45.33 \times 2 \approx 90.7$