A current of 15 A electroplated 50 g of hafnium metal from an aqueous solution in 2hr.

Question

What is the oxidation

of hafnium in the solution?

Answer 1

Moles Hf = 50 g / 178.5 g/mol =0.280

2 h => 7200 seconds

15 A means 15 Coulomb/s

15 Coulomb/s x 7200 =  108000 Coulombs

108000 / 96500 =  1.12 Faradays

1.12 F / 0.280 mol = +4 (number of oxidation )