Standard Reduction Problem

Question

Use the Standard Reduction Potential table to determine if the following reaction will occur spontaneously under standard state conditions.

Br2 (g) + 2Cl− (aq) ↔Cl2 (g) +2Br− (aq)

Answer 1

For questions like these, it is always good to separate the chemical equation into two half reactions/equations. Using the Standard Reduction Table and creating the half reactions, we see that:

Br_{2 (l)} + 2e^- → 2Br^-_(aq) E⁰ = 1.07 V

*Note, bromine should be a liquid in this problem, not a gas, as bromine is a liquid at STP (standard temperature and pressure)*

2Cl^- → Cl_{2 (g)} + 2e^- E⁰ = -1.36 V

By summing the two half-equations above along with their standard potentials, we recover the original chemical equation and a standard electrode potential of:

ΔE⁰ = -0.29 V

Because the value is negative, the reaction will NOT occur spontaneously at STP.