Problem: A disproportionation reaction involves a substance that acts as both an oxidizing and a reducing agent, producing higher and lower oxidation states of the same element in the products. Which of the following disproportionation reactions are spontaneous under standard conditions? Calculate ΔG° and K at 25°C for those reactions that are spontaneous under standard conditions.a. 2Cu+(aq) → Cu 2+(aq) + Cu(s)b. 3Fe2+(aq) → 2Fe 3+(aq) + Fe(s)c. HClO2(aq) → ClO3 -(aq) + HClO(aq) (unbalanced)Use the half-reactions:ClO3- + 3H +  + 2e- → HClO2 + H 2O         ε° = 1.21 VHClO2 + 2H + + 2e- → HClO + H 2O         ε° = 1.65 V

FREE Expert Solution

ΔG° can be calculated from the cell potential using the following equation:

G=-nFE°cell

ΔG° = Gibbs Free Energy, J
n = # of e- transferred
F = Faraday’s constant = 96485 C/(mol e-)
cell = standard cell potential, V

Recall: 1 V = 1 J/C

a.) 2Cu+(aq) → Cu 2+(aq) + Cu(s)

The reaction taking place at cathode is:

Cu+(aq) + e- → Cu(s) E° = 0.52 V

The reaction taking place at anode is:

Cu+(aq) → Cu2+(aq) + e- E° = -0.16 V

E°cell=E°cathode-E°anodeE°cell=0.52 V --0.16 VEcell=0.52 V+0.16 V  

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Problem Details

A disproportionation reaction involves a substance that acts as both an oxidizing and a reducing agent, producing higher and lower oxidation states of the same element in the products. Which of the following disproportionation reactions are spontaneous under standard conditions? Calculate ΔG° and K at 25°C for those reactions that are spontaneous under standard conditions.

a. 2Cu+(aq) → Cu 2+(aq) + Cu(s)

b. 3Fe2+(aq) → 2Fe 3+(aq) + Fe(s)

c. HClO2(aq) → ClO3 -(aq) + HClO(aq) (unbalanced)

Use the half-reactions:

ClO3- + 3H +  + 2e→ HClO2 + H 2O         ε° = 1.21 V

HClO2 + 2H + + 2e→ HClO + H 2O         ε° = 1.65 V


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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Cell Potential concept. If you need more Cell Potential practice, you can also practice Cell Potential practice problems.

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Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl 2nd Edition practice problems.