Question

1. The standard reduction potential for the electrode Sn4+/Sn2+ is 0.16 volts and that of
Fe3+ Fe2+ is 0.77 volts. Write cell reaction and calculate the value of equilibrium
constant at 25 °C.​

Answer 1

The standard reduction potential for the electrode Sn⁴⁺/Sn²⁺ is 0.16V and that of Fe³⁺/Fe²⁺ is 0.77V.

To find : Write the cell reaction and calculate the value of equilibrium.

solution : As $E_{Fe^{3+},Fe^{2+}}$ is higher than $E_{Sn^{4+},Sn^{2+}}$, the cell will be represented as,

$\quad Sn^{2+}|Sn^{4+}||Fe^{3+}|Fe^{2+}$

Therefore the cell reaction will be ...

2Fe²⁺ + Sn²⁺ ⇔2Fe³⁺ + Sn⁴⁺

so, $E_{cell}=E_{Fe^{3+},Fe^{2+}}-E_{Sn^{4+},Sn^{2+}}$

= 0.77 - 0.16

= 0.61 V

now applying Nernst formula,

$\quad K=antilog\left(\frac{nE}{0.0591}\right)$

= antilog(2 × 0.61/0.0591)

= antilog(20.642978)

= 4.39 × 10²⁰

Therefore the equilibrium constant is 4.39 × 10²⁰ .