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Electrochemistry

Question
CBSEENCH12006037

Calculate the standard free energy change for the following reaction at 25°C.
Au(s) + Ca2+(aq.1M) → Au3+(aq. 1M) + Ca(s)
Au2+/Au = – 0.403 V.
Au2+/Cu = – 0.763 V.
Predict whether the reaction will be spontaneous or not at 25°C. Which of the above two half cells will act as an oxidizing agent and which one will be a reducing agent?

Solution
E° = E°Ca2+/Ca - E°Au3+/Au      = -287 - (1.50)      = -2.87 - 1.50 = 4.37 VrG° = nFE°                     

            = 6×96500×(-4.37) = 2530.23 kg