Only Part B needs to be answered Information: Free-energy change, ? G ?, is rela

Question

Only Part B needs to be answered

Information:

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, ?G? must be in joules since 1 J=1 C?V.

Question:

Calculate the standard free-energy change at 25 degree C for the following reaction: Mg(s) + Fe2 + (aq) rightarrow Mg2 + (aq) + Fe(s) Express your answer to three significant figures and include the appropriate units. Calculate the standard cell potential at 25 degree C for the reaction X(s) + 2Y+(aq) rightarrow X2-(aq)+2Y(s) where delta H = -659kJ and delta S degree = -121J/K. Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

PART B

delta Go = delta Ho -T *deltaS

delta Go = -659*1000 J - (298K)(-121 J/K)

delta G0 = -622.94 KJ



dGo = -nFEo

-622.94 kJ = -2 moles of electrons (96.5kJ/mol-ev)(Eo)

Eo = 3.22 volts

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