Problem: Which of the following redox reactions do you expect to occur spontaneously in the reverse direction? [Hint: The reactions are occurring under standard conditions (1 M for the aqueous ions)]a. Ca2+(aq) + Zn(s) → Ca(s) + Zn2+(aq)b. 2 Ag+(aq) + Ni(s) → 2 Ag(s) + Ni2+(aq)c. Fe(s) + Mn2+(aq) → Fe2+(aq) + Mn(s)d. 2 Al(s) + 3 Pb2+(aq) → 2 Al3+(aq) + 3 Pb(s)

FREE Expert Solution

a. Ca2+(aq) + Zn(s)  Ca(s) + Zn2+(aq)


Ca2+ (aq)  Ca (s)

change in O.S. = +2 to 0

decrease/gain electrons  reduction  cathode


Zn (s)  Zn2+ (aq)

change in O.S. = 0 to +2

increase/lose electrons  oxidation  anode


Ca2+ = -2.87 V < E°Zn2+ = -0.76 V 

anode > E°cathode


b. 2 Ag+(aq) + Ni(s) 
 2 Ag(s) + Ni2+(aq)


Ag+ (aq)  Ag (s)

change in O.S. = +1 to 0

decrease/gain electrons  reduction  cathode


Ni (s)  Ni2+ (aq)

change in O.S. = 0 to +2

increase/lose electrons  oxidation  anode


Ag+ = +0.80 V > E°Ni2+ = -0.25 V

anode < E°cathode


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Problem Details

Which of the following redox reactions do you expect to occur spontaneously in the reverse direction? [Hint: The reactions are occurring under standard conditions (1 M for the aqueous ions)]
a. Ca2+(aq) + Zn(s) → Ca(s) + Zn2+(aq)
b. 2 Ag+(aq) + Ni(s) → 2 Ag(s) + Ni2+(aq)
c. Fe(s) + Mn2+(aq) → Fe2+(aq) + Mn(s)
d. 2 Al(s) + 3 Pb2+(aq) → 2 Al3+(aq) + 3 Pb(s)

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