1.

A current of 1.608 A is passed through 250 mL of 0.5 M solution of copper sulphate for 50 minutes. Calculate the strength of Cu^(2+) after electrolysis assuming volume to be constant and the current efficiency is 100%.

Answer»

Solution :`"Given,"I= 1.609A""t="50 min(or)"50xx60=3000S""V=250mL`
`C=0.5M""eta=100%`
The number of Faraday.s of ELECTRICITY passed through the `CuSO_(4)` solution
`rArr""Q=It rArr Q=1.608xx3000`
`Q=4824C`
`therefore"Number of Faraday.s of electricity "=(4824C)/(96500C)=0.5F`
Electrolysis of `CuSO_(4)`
`Cu_((aq))^(2+)+2e^(-)rarrCu_((s))^(-)`.
The above equation shows that 2F electricity will DEPOSIT 1 mole of `CU^(2+)`
`therefore0.5F" electricity will deposit"(1mol)/(2F)xx0.5F="0.025 mol"`
`"Initial number of molar of "Cu^(2+)" in 250 ml of solution"=(0.5)/(1000)xx250mL=0.125mol`
`therefore"Number of molar "Cu^(2+)" after electrolysis "=0.125-0.025=0.1mol`
`therefore"Concentration of "Cu^(2+)=("0.1 mol")/("250 mL")xx"1000 mL"=0.4M`


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