A sphere 100 mm diameter is to be coated with chromium from a solution

containing chromium in the six valent (hexavalent) state. How much time

would be needed to produce a coating 20 micro millimetres thick if;

the current is 20 A

• the cathodic efficiency is 15%

• the atomic weight and density of chromium are 52 and 7.2 gcm respectively

So far Iam working on the basis that the equation to be transposed should be

w=ItA/2F

Any help here would be extremely grateful as I am really struggling with this one. Many thanks.....