Question

Calculate the quantity of electricity required to reduce 6.15 g of nitrobenzene to aniline if the current efficiency is 68 per cent. If potential drop across the cell is 7.0 volts, calculate the energy consumed in the process.

Answer 1

The reduction reaction can be written as:

\[\ce{\underset{1 mole}{C6H5NO2} + 6H+ + \underset{6 moles}{6 e-} -> C6H5NH2 + 2H2O}\]

Molecular mass of nitrobenzene = 123

From the above equation it is clear that one mole (123 g) of nitrobenzene requires 6 moles of electrons for reduction.

∴ Electricity required to reduce 123 g of nitrobenzene = 6 F

= 6 × 96500 C 

Hence, the theoretical quantity of electricity required to reduce 6.15 g of nitrobenzene

= `(6 xx 96500)/123 xx 6.15`

= 28950 C

Since the current efficiency is 68%, the actual quantity of electricity required

= `(28950 xx 100)/68`

= 42573.5 C

Energy consumed = Quantity of electricity × Voltage

= 42573.5 × 7.0

= 298014.5 J

= 298.014 kJ