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Electrochemistry

Question
CBSEENCH12011494
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The standard reduction potential for Zn2+/Zn, Ni2+/Ni and Fe2+/Fe are -0.76, -0.23 and -0.44 V, respectively.

The reaction X + Y2+ → X2+ + Y will be spontaneous when

  • X = Ni, Y = Fe

  • X = Ni, Y = Zn

  • X =Fe, Y = Zn

  • X = Zn, Y = Ni

Solution

D.

X = Zn, Y = Ni

The reaction is spontaneous when ΔG < 0 and E°cell > 0.

∆ G = - nFE° and E° >0Also, Ecell° = Eoxi° + Ered° orEcell° = Ecathode° - Eanode° Here,x + y2+ →     x2+ + yx →   oxidation  x2+y2+ → Reduction  yThus, Ecell° for(a) - 0.21 V, i.e. Ecell° < 0(b) -0.53 V, i.e. Ecell° <0(c)  - 0.32 V, i.e. Ecell° <0(d)  0.53 V, i.e., E°  > 0

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