For the electrochemical reaction between aluminum and tin which has the followin

Question

For the electrochemical reaction between aluminum and tin which has the following cell: Cr_(s) |Cr^3+ (aq) ||Sn^+4 (aq) | Pt_(s). Write the balanced half-cell reactions and the balanced overall reaction. Identify the oxidation and reduction half-cells, as well as the cathode and anode. The standard reduction potentials are -0.74 V for the chromium half-cell and +0.15 V for the tin (Sn) half-cell Determine the standard potential (E degree) for the overall reaction. Is the reaction spontaneous? How can you tell?

Explanation / Answer

IMPORTANT NOTE: this states aluminium and tin, but there is Chromium in the statment, I will assume CHROMIUM

Cr3+ + 3 e Cr(s) 0.74

Sn4+ + 2 e Sn2+ +0.15

a)

balanced reation for this to be spontaneous

2Cr3+ + 6 e 2Cr(s) 0.74

3Sn4+ +6e 3Sn2+ +0.15

Cr is oxidized so

2Cr(s) 2Cr3+ + 6 e 0.74

3Sn4+ +6e 3Sn2+   0.15

Now

E° = Ered + Eox = 0.74 +0.15 = 0.89 V

oxidation is the anode the Cr(s) since it loses electrons

reduction is the cathode, Sn4+, since it gains electrons

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