The electrode reaction is:
Cu2+1 mole+2e−2×96500 C→Cu
63.5 g of copper deposited by passing charge
=2×96500 coulomb
0.635 g of copper deposited by passing charge
=2×9650063.5×0.653 coulomb
=2×965 coulomb
=1930 coulomb
We know that,
Q=I×t
1930=I×60×60
I=19303600=0.536 ampere
∴ Percentage error =(0.536−0.52)0.536×100=2.985.