NCERT chemistry 12th - electrochemistry - intext question 3.4 - Calcul...
Calculation of potential of hydrogen electrode in contact with pH 10 solutionStep 1: Write the half-reaction of the hydrogen electrode
2H+ + 2e- → H2
Step 2: Determine the standard electrode potential of the hydrogen electrode
The standard electrode potential of the hydrogen electrode is 0.00 V at 25°C and 1 atm H2 pressure.
Step 3: Calculate the activity of H+ ions from the given pH value
pH = -log [H+]
[H+] = 10^-pH = 10^-10
Step 4: Calculate the activity of electrons from the Nernst equation
E = E° - (RT/nF) ln Q
At 25°C, R = 8.314 J/K mol, F = 96485 C/mol, n = 2 (since 2 electrons are involved in the half-reaction)
Q = [H+]^2/P(H2), where P(H2) is the pressure of H2 gas (which is 1 atm in this case)
Q = [H+]^2
E = 0.00 - (8.314*298/2*96485) ln (10^-10)^2 = 0.414 V
Step 5: Conclusion
The potential of the hydrogen electrode in contact with a solution whose pH is 10 is 0.414 V. This means that the hydrogen electrode is a reducing agent and has a tendency to donate electrons. It can be used as a reference electrode to measure the potential of other electrodes.