Standard heat of formation of `CH_(4),CO_(2)` and `H_(2)O_((g))` are `-76.2,-394.8` and `-241.6kJ mol^(-1)` respectively. Calculate the amount of heat evolved by burning `1m^(3)` of `CH_(4)` measured under normal conditions.

Explanation

The required equation for the combustion of methane is:
`CH_(4)+2O_(2)toCO_(2)+2H_(2)O,DeltaH=?`
`DeltaH=DeltaH_(f("products"))-DeltaH_(f("reactants"))`
`=DeltaH_(f(CO_(2)))+2xxDeltaH_(f(H_(2)O)-DeltaH_(f(CH_(4)))-2DeltaH_(f(O_(2)))`
`=-398.8-2xx241.6-(-76.2)-2xx0`
`=-805kJ" "mol^(-1)`
heat evolved by burning 22.4 litre (1 mole) methane `=-805.8kJ`. So, heat evolved by burning 1000 litre `(1m^(3))` methane
`=-(805.8)/(22.4)xx1000=-35973.2kJ`