The standard electrode potentials of Z n 2 + | Z n , C u 2 + | C u a n d A g + | A g are respectively - 0.76…

The standard electrode potentials of



Zn2+ | Zn , Cu2+ | Cu and Ag+ | Ag are respectively - 0.76, 0.34 and 0.8 V. The following cells were constructed



I -  Zn | Zn2+ ||  Cu2+ | Cu



II -  Zn | Zn2+ ||  Ag+ | Ag



III - Cu | Cu2+ || Ag+ | Ag



What is the correct order of Ecell° of these cells?
  1. II > III > I
  2. II > I > III
  3. I > II > III
  4. III > I > II

Solution

Given,

Zn 2+ + 2e    Zn ,        E ° =0.76 V

Cu 2+  + 2e   Cu ,       E °  = 0.34 V

Ag +   + e  Ag ,         E °  = 0.8 V

Cell reaction of (I) is

Zn + Cu2+  Zn2+ + Cu

Ecello=Eredo(cathode)-Eredo(anode)
=0.34 0.76 =1.10V

Cell reaction of (II) is

Zn +  2Ag +    Zn 2+  + 2Ag

E Cell o =+0.80 0.76 =+1.56V

Cell reaction of (III) is

Cu +  2Ag +    Cu 2+  + 2Ag

E Cell o =+0.80 0.34 =+0.46V

So, the correct order of Ecell° of these cell is

II > I > III. *

Asked in: JEE-TOPICTESTS-CHEMISTRY

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