Question

For hydrogen-oxygen fuel cell, the cell reaction is $2H_2(g)+O_2(g)\rightarrow2H_2O(I)$, If $\triangle{G}\degree_{f}(H_2O)=-237.2KJmol^{-1}$ then emf ofthis cell is

• A. + 2.46 V
• B. - 2.46 V
• C. + 1.23 V
• D. - 1.23 V

Answer 1

Answer: (C)

+ 1.23 V

Answer 2

Formula for gibbs free energy= $-nFE$
$Emf = \frac{ΔG}{nF}$
$ΔG = 237.2kJ/mol$
$n= 2$
Substituting the values
$Emf = 237.2\times \frac{1000}{2} \times 96500 =1.23V$