Question

Given:

Cr3+(aq)+3e– ⇌Cr(s);E°=−0.74V

Sn4+(aq)+2e– ⇌Sn2+(aq);E°=0.15V

What is the standard cell potential for the following reaction?

3Sn4+(aq) + 2Cr(s) ⇔3Sn2+(aq) + 2Cr3+(aq)

Select one:

a. 0.89 V

b. −0.59 V

c. 0.59

d. −0.89 V

e. 0 V

Answer 1

Given that  

3Sn⁴⁺_(aq) + 2Cr(s)  ⇔ 3Sn²⁺ (aq) + 2Cr⁺³(aq)

From the equation, we can see that Sn is reduced ( electron gain) and Cr is oxidized (electron loss)and we know oxidation occurs at anode and reduction occurs at the cathode in the cell.

We know that E⁰_cell = E⁰_R - E⁰_L

where  E⁰_cell = Standared reduction potential of Sn and  E⁰_L = standared reduction potential of Cr

Therefore

E⁰_cell = 0.15 - (-0.74)

E⁰_cell = 0.89V

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