Question

The number of electrons involved in the electro deposition of 63.5g of Cu from a solution of CuSO4 is

1)6.0×10(23) 2)3.011 ×10(23). 3)12.04×10(23) 4)6.02×10(22) (the ones in the brackets the powers)

Answer 1

3)12.04×10(23


This is a redox reaction, meaning reduction-oxidation reaction. This represents the reaction in one side of the electrode in an electrolysis set-up. First, we find the oxidation number of Cu in CuSO4:

(ox. # of Cu)+ ox.# of S + 4(ox.# of oxygen) = 0
(ox. # of Cu) + (6) + 4(-2) = 0
ox. # of Cu = 2+

CuSO4 ---> Cu + SO42-
Cu2+ + SO42- ----> Cu + SO42-
Cu2+ -----> Cu + 2e- (net ionic reaction)

The stoichiometric equation would be 2 electrons per mole Copper. Copper has a molar mass of 63.5 g/mol. Then, it would only need 2 moles electrons.
that is 2*6.022*10(23)=12.04×10(23)