Question

For a silver- magnesium voltaic cell,calculate the standard emf $\left(E_{cell}^0\right)$

$M{g}^{2+}+2e^{-}\to Mg\left(s\right);E^0=-2.37V$
$A{g}^{+}\left(aq\right)+e^{-}\to Ag\left(s\right);E^0=+0.80V$

• A. $3.17V$
• B. $-3.17V$
• C. $1.57V$
• D. $-1.57V$

Answer 1

The correct option is A $3.17V$

The standard reduction potential of silver is higher than magnesium.
Thus,
Cathode reaction is
$A{g}^{+}\left(aq\right)+e^{-}\to Ag\left(s\right)$

Anode reaction is
$Mg\left(s\right)\to M{g}^{2+}+2e^{-}$

$E_{cell}^0=\text{SRP of substance reduced}-\text{SRP of substance oxidised}$
(SRP - Standard reduction potential)

$E_{cell}^0=E_{cathode\left(red\right)}^0-E_{anode\left(red\right)}^0$

$E_{cell}^0=0.80+2.37=3.17V$