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, 0.34 and 0.8 V. The following cells were constructed I - Z n | Z n 2 + | | C u 2 + | C u II - Z n | Z n 2 + | | A g + | A g III - C u | C u 2 + | | A g + | A g What is the correct order of E c e l l ° of these cells?

Step-by-step 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 Z n + C u 2 + → Z n 2 + + C u E cell o = E red o ( cathode ) - E red o ( anode ) = 0.34 − − 0.76 = 1.10 V Cell reaction of (II) is Zn + 2Ag + → Zn 2 + + 2Ag E Cell o = + 0.80 − − 0.76 = + 1.56 V Cell reaction of (III) is Cu + 2Ag + → Cu 2 + + 2Ag E Cell o = + 0.80 − 0.34 = + 0.46 V So, the correct order of E c e l l ° of these cell is II > I > III.