Question

The standard reduction potentials for Zn2+/Zn, Ni2+/Ni and Fe2+/Fe are –0.76, – 0.23 and –0.44 V respectively. The reaction X + Y2+$\rightarrow$ X2+ + Y will be spontaneous, when :

• A. X = Ni, Y = Fe
• B. X = Ni, Y = Zn
• C. X= Fe, Y = Zn
• D. X= Zn, Y = Ni

Answer 1

Answer: (D)

X= Zn, Y = Ni

Answer 2

$\text{X + }\text{Y}^{\text{2+}}\overset{\quad\quad}{\rightarrow}X^{\text{2+}}\text{ + Y}$For reaction to be

spontaneous Eº must be positive.

$E_{\text{Zn / Zn+2}}^{0}\text{ + }\text{E}_{\text{Ni2+ / Ni}}^{0}\text{ = 0.76 + }(\text{- 0.23})\text{ = + 0.53}$ (positive)