Feasibility of redox reactionsEdexcel International A Level Chemistry: Flashcards

What these 12 flashcards ask

When is a redox reaction feasible under standard conditions?
How do you calculate E°cell for a reaction?
What is disproportionation?
Give the equation for disproportionation of copper(I).
What is the link between E°cell and total entropy change?
What is the link between E°cell and K?
What does a positive E°cell tell you about K?
What does E°cell say about the rate of a reaction?
What is kinetic stability?
Give an example of a feasible reaction that is kinetically stable.
Why can MnO₂ and concentrated HCl make Cl₂ although E°cell is −0.13 V?
Why are predictions from E° limited?

Exam questions on Feasibility of redox reactions

Standard electrode potentials: Cl₂(g)|Cl⁻(aq) +1.36 V; Br₂(aq)|Br⁻(aq) +1.09 V; I₂(aq)|I⁻(aq) +0.54 V.
Chlorine water is added to aqueous potassium bromide. Calculate E°cell for the reaction and state whether it is feasible.2 marks
Copper(I) ions in aqueous solution can undergo disproportionation. Standard electrode potentials: Cu²⁺(aq) + e⁻ ⇌ Cu⁺(aq) +0.15 V; Cu⁺(aq) + e⁻ ⇌ Cu(s) +0.52 V.
Use the data to show that copper(I) ions disproportionate in aqueous solution under standard conditions.2 marks
The reaction 2Fe³⁺(aq) + 2I⁻(aq) → 2Fe²⁺(aq) + I₂(aq) is studied at 298 K. Standard electrode potentials: Fe³⁺(aq)|Fe²⁺(aq) +0.77 V; I₂(aq)|I⁻(aq) +0.54 V. Use F = 96 500 C mol⁻¹ and R = 8.31 J K⁻¹ mol⁻¹. For a cell reaction in which n electrons are transferred: ΔS_total = nFE°cell / T and ln K = nFE°cell / (RT).
Calculate E°cell and the total entropy change for this reaction at 298 K.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).