Question

The standard reduction potentials of $Mg,Zn,Ni,H_2,Cu$ and $Ag$ are $-2.37,-0.76,-0.25,0.00,0.034$ and $0.80$ volt respectively. Which one of the following cells has maximum voltage?

• A. $Mg+2A{g}^{+}\to M{g}^{2+}+2Ag$
• B. $C{u}^{2+}+H_2\to Cu+2H^{+}$
• C. $Ni+C{u}^{2+}\to N{i}^{2+}+Cu$
• D. $Zn+2A{g}^{+}\to Z{n}^{2+}+2Ag$

Answer 1

Answer: (A)

$Mg+2A{g}^{+}\to M{g}^{2+}+2Ag$

$E_{cell}^{\circ }=E_c-E_a=0.80-(-2.37)=+3.17V$

$C{u}^{2+}+H_2\to Cu+2H^{+}$

$E_{cell}^{\circ }=0.034-0=+0.034V$

$Ni+C{u}^{2+}\to N{i}^{2+}+Cu$

$E_{cell}^{\circ }=0.034-(-0.25)=0.284V$

$Zn+2A{g}^{+}\to Z{n}^{2+}+2Ag$

$E_{cell}^{\circ }=0.80-(-0.76V)=1.56V$