1 litre aqueous solution of NaCl was electrolysed bètweern Pt electrodes passing a direct current of 12.87 A for 100s with a current efficiency of 75%. Calculate pH of the solution after electrolysis assuming no change in volume of solution.

Options

A. `5 xx 10^(-3)` M
B. `5 xx 10^(-2) M`
C. `0.5 xx 10^(-3)` M
D. `1.0 xx 10^(-2) M`

Answer

D

Explanation

`I = 1 A `, t = 16 min 5 s = 965 s
Quantity of electricity passed = `I xx t`
= `1 xx 965 = 965` C
w = ZIT
`w = (12)/(96500) xx 965 = (12)/(100)` g
Conc., of `MgCl_2 = ("Weight")/("Mol wt" xx "V (in L)")`
`= (12)/(100 xx 24 xx 1) = 5 xx 10^(-3) M`