Question

Calculate the standard enthalpy change for the a cell reaction which has a standard cell potential of $1.50V$. The cell reaction involves the transfer of 2 moles of electrons and standard entropy change is $110J{K}^{-1}$.

• A. $-297kJ$
• B. $-257kJ$
• C. $-144kJ$
• D. $123kJ$

Answer 1

The correct option is B $-257kJ$

We know,
$\Delta G^o=-nF{E}^o=-2\times 96500\times 1.50=-289500J=-289.5kJ$

$\Delta S^o=110J/K=0.11kJ/K$

$\Delta G^o=\Delta H^o-T\Delta S^o$
$\Delta H^o=\Delta G^o+T\Delta S^o$
$\Delta H^o=-289.5+(298\times 0.11)$
$\Delta H^o=-289.5+32.78$
​​​​​​​$\Delta H^o=-256.72kJ$