Question

Efficiency of the following cell is 84 %.
$A\left(s\right)+B^{2+}(aq.)\rightleftharpoons A^{2+}(aq.)+B\left(s\right);\Delta H^o$ = -285kJ. Then the standard EMF of the cell will be:

• A. 2.2 V
• B. 2.40 V
• C. 0.9 V
• D. 1.24 v

Answer 1

The correct option is D 1.24 v

$A+B^{+2}\rightleftharpoons A^{+2}+Bn=2$

$\Delta 4=\Delta -T\Delta S$

$\Delta s=0$

$\Delta 4=\Delta H=-2gskg$

$\Delta 4=-nF{E}_{cell}^o$

$E_{cell}^o=\frac{\Delta 4}{-nF}=\frac{-285\times 1000}{96500\times 2}$

$E_{cell}=1.4767$

$E_{cell}=\frac{1.4767\times 84}{100}=1.24V$