Calculate E°, identify the cathode and anode, and give the overall balanced equation.

Question

Calculate E°, identify the cathode and anode, and give the overall balanced equation. Assume that all concentrations are 1.0 M and that all partial pressures are 1.0 atm. Standard reduction potentials are found in a Standard Reduction Potentials table. (Use the lowest possible whole number coefficients. Include states-of-matter under the given conditions in your answer.)

Ni^2+(aq) + Al(s) → Al^3+(aq) + Ni(s)

Ni^2+ +2e^- —>Ni   E=-0.23   

Al^3+ + 3e^- —>Al   E= -1.66

E° was calculated to be 1.43 V

Ni is cathode  

Al is anode 

How do I figure out the balanced equation? I am extremely confused and I think I’m seeing it harder than it actually is. Thanks 



Initially I got Ni^2+ +Al —>Al^3+ + Ni but I’m missing something in balancing it out. 

Answer 1

For the balanced equation you need to include the net electron transfer (also the states of matter, as specified in the question).

Thus,

Ni²⁺_(aq) + Al_(s) → Al³⁺_(aq) + Ni_(s) + 1 e^-

Answer 2

Ni^2+ +2e^- —>Ni   E=-0.23   

Al^3+ + 3e^- —>Al   E= -1.66

Ni2+ + 2e- ==> Ni(s) [x3]

Al(s) ==> Al3+ + 3e- [x2]

3Ni²⁺ + 6e- = 3Ni(s)

2Al(s) ==> 2Al³⁺ + 6e-

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3Ni²⁺⁽aq) + 2Al(s) ==> 3Ni(s) + 2Al³⁺(aq) This is the balance equation.