chem help?

2020-04-27 12:20 pm

Use standard reduction potentials to calculate the standard free energy change in kJ for the reaction:

Cd2+(aq) + Cu(s) Cd(s) + Cu2+(aq)

______ kJ

K for this reaction would be (less or greater) than one

回答 (1)

胡雪8°

2020-04-27 4:10 pm

✔ 最佳答案

Refer to: http://www2.ucdsb.on.ca/tiss/stretton/database/Standard_Reduction_Potentials.htm
Cd²⁺(aq) + 2e⁻ → Cd(s) E° = -0.40 V
Cu²⁺(aq) + 2e⁻ → Cu(s) E° = +0.34 V

Consider the cell reaction:
Cd²⁺(aq) + Cu(s) → Cd(s) + Cu²⁺(aq)
E°cell = E°(red) - E°(oxid) = (-0.40) - (+0.34) = -0.74 V

ΔG° = -n F E°(cell)
Standard free energy change, ΔG° = -2 × 96485 × (-0.74) J = +143000 J = +143 kJ

ΔG° = -R T ln(K)
Then, ln(K) = - R T / ΔG°
Since R > 0, T > 0 and ΔG° > 0, ln(K) = - R T / ΔG° < 0
Hence, K < 1

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