In a fuel cell, methanol is used as fuel and oxygen gas is used as an oxidiser. The reaction $$isCH3OHl$$ $$+32O2g$$ →$$CO2g$$ $$+2H2OlAt$$ $$298$$ K standard Gibbs energies of formation for $$CH3OHl$$, $$H2Ol$$ and $$CO2g$$ are $$-166.2$$, $$-237.2$$ and $$-394.4$$ kJ $$mol-1$$, respectively. If standard enthalpy of combustion of methanol is $$-726$$ kJ $$mol-1$$, efficiency of the fuel cell will be

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In a fuel cell, methanol is used as fuel and oxygen gas is used as an oxidiser. The reaction $$isCH3OHl$$ $$+32O2g$$ →$$CO2g$$ $$+2H2OlAt$$ $$298$$ K standard Gibbs energies of formation for $$CH3OHl$$, $$H2Ol$$ and $$CO2g$$ are $$-166.2$$, $$-237.2$$ and $$-394.4$$ kJ $$mol-1$$, respectively. If standard enthalpy of combustion of methanol is $$-726$$ kJ $$mol-1$$, efficiency of the fuel cell will be

Infinity Learn · Accepted Answer

Percentage efficiency of the fuel cell $$=$$ ∆G∆H×$$100$$. The concerned reaction is $$CH3OHl$$ $$+32O2g$$ →$$CO2g$$ $$+2H2Ol$$∆$$Gr=$$∆Gf $$CO2$$, g $$+$$ $$2$$∆Gf $$H2O$$, $$l-$$                                                             ∆$$GrCH3OH$$, $$l+32$$∆Gf O, g $$=-394.4$$ $$+2-237.2$$ $$-$$ $$-166.2-0$$ $$=-394.4-474.4+166.2=-702.6$$ kJ $$mol-1$$ Percentage efficiency $$=$$ $$702.6726$$× $$100=96.78$$%≈$$97$$%

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