Question

Salts of A (atomic mass 15), B (atomic mass 27) and C (atomic mass 48) were electrolysed using same amount of charge. It was found that when 4.5 g of A was deposited, the masses of B and C deposited were 2.7 g and 9.6 g. The valencies of A, B and C were respectively

• A. 1, 3 and 2
• B. 3, 1 and 3
• C. 3, 1 and 2
• D. 2, 3 and 2

Answer 1

Answer: (C)

According to Faraday's second law

$\frac{\text{Mass}\text{of}\text{A}}{\text{Equivalent}\text{mass}\text{of}\text{A}}\text{=}\frac{\text{Mass}\text{of}\text{B }}{\text{Equivalent}\text{mass}\text{of}\text{B}}\text{=}\frac{\text{Mass}\text{of}\text{C}}{\text{Equivalent}\text{mass}\text{of}\text{C}}$

$\frac{4.5}{15/n_1}=\frac{2.7}{27/n_2}=\frac{9.6}{48/n_3}$

$n_1:n_2:n_3$

$0.3:0.1:0.2$

$3:1:2$ .