In a fuel cell methanol is used as fuel and oxygen gas is used as an oxidizer. The reaction is `:`
`CH_(3)OH_((l))+(3)/(2)O_(2(g))rarr CO_2((g))+2H_(2)O_((l))`
At `298K` standard Gibb's energies of formation for `CH_(3)OH(l), H_(2)O(l)` and `CO_(2)(g)` are `-166.2,-237.2` and `-394.4kJ mol^(-1)` respectively. If standard enthalpy of combustion of methanol is `-726kJ mol^(-1)`, efficiency of the fuel cell will be `:`

Options

A. 0.8
B. 0.87
C. 0.9
D. 0.97

Answer

D

Explanation

`DeltaG_(f)^(@)(O_(2))=0`. Calculate `DeltaG_(f)^(@)` reaction and then apply : Efficiency `(DeltaG^(@))/(DeltaH^(@))xx100`.