DeltaGdegree and Edegree can be said to measure the same thing, and are converti

Question

DeltaGdegree and Edegree can be said to measure the same thing, and are convertible by the equation AGdegree = -nFEdegree_cell where n is the total number of moles of electrons being transferred, and F is the Faraday constant 9.64853415 Times 10^4 C/mol. The free energy (DeltaGdegree) of a spontaneous reaction is always negative. For each of the electrochemical cells below, calculate the free energy of the system and state whether the reaction is spontaneous or non-spontaneous as written based on the cathode and anode assignment given. (Use the table of Standard Electrode Potentials.) (a) The cathode is Co(II) and the anode is Zn(II). free energy spontaneity spontaneous (b) The cathode is Cd(II) and the anode is Sn(II). free energy kJ spontaneity non-spontaneous (c) The cathode is Cr(III) and the anode is Ti(III). free energy kJ spontaneity spontaneous

Explanation / Answer

a)

cathode is Co(II) potential = - 0.28

anode is Zn(II) potential = - 0.76

Eo cell = Eocathode - E anode

            = - 0.28 - (- 0.76)

            = 0.48 V.

delta Go = - n F Eo cell

               = - 2 x 96485 x 0. 48

delta Go = - 92.63 kJ

b)

cathode Cd(II) = - 0.403

anode Sn(II) = - 0.14

Eo cell = - 0.14 + 0.403

            = - 0.263 V.

delta Go = - n F Eo cell

               = - 2 x 96485 x - 0. 263

                = + 50.75 kJ

c)

cathode is Cr(III) potential = - 0.74

anode is Ti(III) potential = - 1.63

Eo cell = Eocathode - E anode

            = - 0.74 - (- 1.63)

            = 0.89 V.

delta Go = - n F Eo cell

               = - 3 x 96485 x 0. 89

delta Go = - 257.6 kJ

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