Electrolysis of copper sulphate solution using platinum anode and…

MCQ

Electrolysis of copper sulphate solution using platinum anode and copper or platinum cathode which of the following statement regarding the electrolysis is correct?
P: When the deposition of Cu ions is completed then electrolysis of water takes place
Q : The blue colour of $Cu ^{2+}$ ions in the electrolyte solution fades.

A
Only P
B
Only Q
C
Both P & Q
D
Neither P nor Q

✓

Answer

C. Both P & Q
Explanation: When deposition of Cu is completed then electrolysis of water takes place. Hydrogen gas is liberated at the cathode and oxygen gas is liberated at the anode while the blue colour of $Cu ^{2+}$ ions in electrolyte solution fade due to decrease in $Cu ^{2+}$ ions and finally the solution becomes colourless as soon as $Cu ^{2+}$ ions are finishedDissociation of aq. $CuSO _4$ solution
$CuSO _4 \quad Cu ^{2+}+ SO _4{ }^{2-}$
$H _2 O \quad H ^{+}+ OH ^{-}$
Ions present: $Cu ^{2+}, H ^{+}, SO _4{ }^{2-}, OH ^{-}$
At cathode : $Cu ^{2+}+2 e^{-} \rightarrow Cu ^{-}$
At anode : $4 OH ^{-}-4 e^{-} \rightarrow 4 OH$
$2 OH+2 OH \rightarrow 2 H_2 O+O_2$

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