How to Calculate the pH of the Solution at an Electrode – Part 1

Electromotive force (EMF) or electromotance is an energy transfer to an electric circuit per unit of electric charge.


An electrochemical cell is a device that either generates electrical energy from chemical reactions in a so-called galvanic or voltaic cell, or induces chemical reactions (electrolysis) by applying external electrical energy in an electrolytic cell.

The Nernst equation is a chemical thermodynamical relationship which allows the calculation of the reduction potential of a (half-cell/full-cell) reaction from the standard electrode potential, absolute temperature, the number of electrons involved in the redox reaction, and activities (often approximated by concentrations) of the chemical species undergoing reduction and oxidation respectively.

Mnemonic: An Ox, Red Cat (Anode Oxidation, Reduction Cathode)

Question:

The EMF of a cell corresponding to the reaction

Zn(s) + 2H+(aq) → Zn2+ (0.1 M) + H2(g) (1 atm)

is 0.28 V at 250C. Calculate the pH of the solution at the H-electrode. EѲ(H+/H2) = 0, EѲ(Zn2+/Zn) = ─ 0.76 V

Solution:



Click/tap to enlarge the image

E = Cell potential, EѲ = Standard cell potential, n = Number of electrons in the balanced half-cell equation, Q = Reaction quotient

Electrified by electrochemistry❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

(1)    Wikipedia Contributors. Electromotive force. Wikipedia. https://en.wikipedia.org/wiki/Electromotive_force.

‌(2)    Wikipedia Contributors. Electrochemical cell. Wikipedia. https://en.wikipedia.org/wiki/Electrochemical_cell.

‌(3)    Wikipedia Contributors. Nernst equation. Wikipedia. https://en.wikipedia.org/wiki/Nernst_equation.

(4)    Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

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