If the pressure of H 2 gas is increased from 1 atm to 100 atm keeping H + concentration constant at 1 M , the change in reduction potential of hydrogen half cell at 2 5 ∘ C will be

Question

If the pressure of H 2 ​ gas is increased from 1 atm to 100 atm keeping H + concentration constant at 1 M , the change in reduction potential of hydrogen half cell at 2 5 ∘ C will be

TestHub · Accepted Answer

The half-cell reaction for a hydrogen half-cell acting as a cathode is $2 H^{+} + 2 e^{-} ⟶ H_{2}$ .

Therefore,

$E_{H^{+} ∣ H_{2}} = E_{H^{+} ∣ H_{2}}^{\circ} - \frac{0.059}{2} lo g \frac{P _{H_{2}}}{[ H ^{+} ] ^{2}}$

$E_{H^{+} ∣ H_{2}} = - \frac{0.059}{2} lo g \frac{1}{[ H ^{+} ] ^{2}}$

Now, when the pressure of H₂ gas is changed to 100 atm without changing $[H^{+}]$ , the reduction potential becomes

$E_{H^{+} ∣ H_{2}}^{'} = - \frac{0.059}{2} lo g \frac{100}{[ H ^{+} ] ^{2}}$

Change in reduction potential = $E_{H^{+} ∣ H_{2}}^{'} - E_{H^{+} ∣ H_{2}} = - \frac{0.059}{2} lo g (\frac{100}{[ H ^{+} ] ^{2}} \times \frac{[ H ^{+} ] ^{2}}{1})$

$= - 0.059 V$

Chemistry - Electrochemistry Question with Solution | TestHub

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