Use tabulated electrode potentials to calculate ∆g° rxn for each reaction at 25 °c in kj.
(a) pb2+(aq) + mg(s) ➝ pb(s) + mg2+(aq)
(b) br2(l) + 2 cl-(aq) ➝ 2 br-(aq) + cl2( g)
(c) mno2(s) + 4 h+(aq) + cu(s) ➝ mn2+(aq) + 2 h2o(l) + cu2+(aq)

(a) , (b) and (c)  

Explanation: (a) Oxidation half reaction for the given equation is:

The reduction half equation is:

where n is the number of moles of electrons transferred and F is faraday constant.

2 moles of electrons are transferred in the cell reaction which is also clear from both the half equations.

or

(b) Oxidation half reaction for the given equation is:

Reduction half equation is:

Now, we can calculate the same as we did for part a.

or

(c) Oxidation half reaction for the given equation is:

reduction half equation is:

or