Question

Standard free energies of formation(in $kJ/mol$) at $298$K are $-237.2$, $-394.4$ and $-8.2$ for $H_{2}O\left(I\right),C{O}_2\left(g\right)$ and pentane(g) respectively. The value of $E_{cell}^o$ for the pentane-oxygen fuel cell is:

• A. $1.968$V
• B. $2.0968$V
• C. $1.0968$V
• D. $0.0968$V

Answer 1

The correct option is C $1.0968$V

Pentane $-C_5{H}_{12}$

$C_5{H}_{12}+8O_2\to 5C{O}_2+6H_{2}O$

$\Delta G^{\circ }\left(298K\right)$$=5(-394.4)+6(-237.2)-(-8.2)$

$=-3387\times {10}^{3}J/mole$

$\Delta G^{\circ }=nF{E}_{cell}^{\circ }$

$n=5\times 4+6\times 2=32$

$\Delta E_{cell}^{\circ }=\frac{(3387\times {10}^3)}{(32\times 96500)}$

$=1.0968V$