In a fuel cell (device used for producing electricity directly from a chemical reaction )methanol is used as a fuel and oxygen gas is used asan oxidizer. The standard enthalpyof combustion of methanol is -721kJ mol^(-1) . The standard free energiesof formation of CH_(3)OH(l, CO_(2)(g) andH_(2)O(l) are- 166.3 , -394.4 and - 237 .1 kJ mol^(-1) respectively. The standard free energy change of the reaction will be

In a fuel cell (device used for producing electricity directly from a

1.	In a fuel cell (device used for producing electricity directly from a chemical reaction )methanol is used as a fuel and oxygen gas is used asan oxidizer. The standard enthalpyof combustion of methanol is -721kJ mol^(-1) . The standard free energiesof formation of CH_(3)OH(l, CO_(2)(g) andH_(2)O(l) are- 166.3 , -394.4 and - 237 .1 kJ mol^(-1) respectively. The standard free energy change of the reaction will be
Answer» `-597.8 kJ mol^(-1)` `-298 kJmol^(-1)` `- 465.2 kJ mol^(-1)` `-702.3kJ mol^(-1)` Solution :The reaction is `CH_(3)OH(l) + (3)/(2) O_(2)(g) rarr CO_(2)(g) + 2H_(2)O(l) ` `Delta_(R)G^(@) = SigmaDelta_(f)G^(@)(` PRODUCTS) - `SigmaDelta_(f)G^(@)(`REACTANTS) `= [ Delta_(f)G^(@) ( CO_(2) +2Delta_(f) G^(@) (H_(2)O)] -[Delta_(f)G^(@) (CH_(3)OH)+(3)/(2)Delta_(f)G^(@) (O_(2))]` `= [( - 394.4) + 2 ( - 237.1) ] - [ - 166.3 + (3)/(2) (0)]` `=- 702 . 3 kJ mol^(-1)`