Standard reduction potentialsReduction half-reactionE ? (V )Ag + (aq)+e ? ?Ag(s)

Question

Standard reduction potentialsReduction half-reactionE ?   (V )Ag + (aq)+e ? ?Ag(s)       0.80 Cu 2+ (aq)+2e ? ?Cu(s)       0.34 Sn 4+ (aq)+4e ? ?Sn(s)       0.15 2H + (aq)+2e ? ?H 2 (g)       0 Ni 2+ (aq)+2e ? ?Ni(s)       ? 0.26Fe 2+ (aq)+2e ? ?Fe(s)       ? 0.45Zn 2+ (aq)+2e ? ?Zn(s)       ? 0.76Al 3+ (aq)+3e ? ?Al(s)       ? 1.66Mg 2+ (aq)+2e ? ?Mg(s)       ? 2.37

Part A Use the table of standard reduction potentials given above to calculate the equilibrium constant at standard temperature (25  ? C ) for the following reaction: Fe(s)+Ni 2+ (aq)?Fe 2+ (aq)+Ni(s)    Express your answer numerically.

Part B Calculate the standard cell potential (E ?  ) for the reaction X(s)+Y + (aq)?X + (aq)+Y(s)    if K  = 1.12

Explanation / Answer

Fe(s)+Ni 2+ (aq)?Fe 2+ (aq)+Ni(s)

From the table,

Fe 2+ (aq)+2e ? ?Fe(s) ? 0.45

Ni 2+ (aq)+2e ? ?Ni(s) ? 0.26

So,

E= 0.45-0.26 =0.19 V

ln k=nFE/RT

k=10^(2*190/59.2)=2.6*10^6

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Part B

K = 1.12

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