The heat of combustion of `H_(2)(g)` at constant pressure and `300k` is `-280kJ mol^(-1)`. What will be the heat of combustion at constant volume and at `300K`?

Explanation

`H_(2)(g) = (1)/(2)O_(2)(g) rarr H_(2)O(l) DeltaH =- 280 kJ mol^(-1)`
`DeltaH = DeltaU +DeltanRT, Deltan = 0 - (3)/(2) =- (3)/(2)`,
`DeltaH = DeltaU -(3)/(2) xx 8.314 xx 300`
`- 280 kJ = DeltaU - (74826)/(20) xx (1)/(1000) kJ`
`rArr DeltaU =- 276.2587 kJ`