 Solution

ID: past-exam-of-the-chemistry-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2025/4/b/ii/solution

The Nernst equation for the six-electron cell reaction is

E = E^{\circ} - \frac{RT}{6 F} ln Q, Q = \frac{a _{Z n^{2 +}}^{3} a _{NO}^{2}}{a _{N O_{3}^{-}}^{2} a _{H^{+}}^{8}} .

a_{NO} = p_{NO} / p^{\circ}

with

p^{\circ} = 1 bar

; for ideal dissolved species,

a_{i} = [i] / c^{\circ}

. The reaction quotient is dimensionless. The platinum supplies an electronically conducting surface and is absent from the net chemical equation.

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