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Problems and Solutions

Problem :

Given that the free energy of formation of liquid water is -237 kJ / mol, calculate the potential for the formation of hydrogen and oxygen from water.

To solve this problem we must first calculate ΔG for the reaction, which is -2 ( -237 kJ / mol) = 474 kJ / mol. Knowing that ΔG = -nFEo and n = 4, we calculate the potential is -1.23 V.

Problem :

Calculate the potential of a concentration cell with anode concentration of 1 M and cathode concentration of 0.01 M at 75oC.

Knowing the Nernst Equation and realizing that the temperature is not 25oC, we write that: E = Eo - (RT/nF) ln Q Eo for any concentration cell is zero so, after plugging in all the numbers we find that: E = 0.035 V.