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. `80%`
B. `87%`
C. `97%`
D. `90%`

Answer

C

Explanation

`eta=(DeltaG)/(DeltaH),DeltaG=SigmaDeltaG_(f)^(@)("products")`
`-SigmaDeltaG_(f)^(@)("reactants")=-395.4-2(237.2)+166`
`=-702"KJ/Mole"`
`eta =(702.6) /(726) xx100=97%`