A solution of `Ni(NO_3)_2` is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?

Explanation

I=5.0 A, t=30 min=`30xx60s=1800s`
`Q=IxxT=5.0Axx1800s=9000C`
`Ni(NO_(3))_(2)hArr Ni^(2+)+2NO_(3)^(-)`
`Ni^(2=)+underset(2mol)(2e^(-))to underset(1mol)(Ni)`
Thus 2 mol or electrons are required to depsit 1 mol or 58.5 g of Ni.
charge on 2 mol of electrons
`=(2molxx96500C" "mol^(-1))`
`=193,000C`
`193000C` of electricity deposit Ni=58.5 g
9000 C electricity will deposit Ni
`=(58.5xx9000)/(1,93,000)`
`=2.73g`