Question

A Cr3+(aq) solution is electrolyzed, using a current of 7.80 A .

1. What mass of Cr(s) is plated out after 1.50 days?

2.What amperage is required to plate out 0.200 mol Cr from a Cr3+ solution in a period of 7.00 h ?

Answer 1

1) 7.80A = 7.80 Coulomb per second

Coulomb in 1.50 days = 129600 × 7.80 = 1010880C

No of mole of electron = 1010880/96485 = 10.477

No of mole of electron required to deposit 1mol of Cr = 3

No of mole of Cr3+ deposited = 10.477/3= 3.4923

molar mass of Cr = 51.996g/mol

Mass of Cr plated = 51.996g/mol × 3.4923mol = 181.59g

2) mole of Cr plated out = 0.200mol

mole of electron required = 3×0.2 = 0.6mol

Coulombs required = 0.6 × 96485 = 57891C

plating period = 7 hours = 25200seconds

Amperage required = 57891/25200=2.297A