Free-energy change, ? G ?, is related to cell potential, E ?, by the equation ?

Question

Free-energy change, ?G?, is related to cell potential, E?, by the equation

?G?=?nFE?

where n is the number of moles of electrons transferred and F=96,500C/(mol e?) is the Faraday constant. When E? is measured in volts and can be determined from half-reaction potentials as given in the table below. ?G?must be in joules since 1 J=1 C?V.

A) Calculate the standard free-energy change at 25 ?C for the following reaction using the table in the introduction: Mg(s)+Fe2+(aq)?Mg2+(aq)+Fe(s)

Express your answer numerically in joules.

B)

Calculate the standard cell potential at 25 ?C for the reaction

X(s)+2Y+(aq)?X2+(aq)+2Y(s)

where ?H? = -675kJ and ?S? = -121J/K .

Express your answer numerically in volts.

Reduction half-reaction E? (V) Ag+(aq)+e??Ag(s) 0.80 Cu2+(aq)+2e??Cu(s) 0.34 Sn4+(aq)+4e??Sn(s) 0.15 2H+(aq)+2e??H2(g) 0 Ni2+(aq)+2e??Ni(s) ?0.26 Fe2+(aq)+2e??Fe(s) ?0.45 Zn2+(aq)+2e??Zn(s) ?0.76 Al3+(aq)+3e??Al(s) ?1.66 Mg2+(aq)+2e??Mg(s) ?2.37

Explanation / Answer

The half reactions involved of this redox reaction and their respective standard electrode potentials are:
(1) Mg

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