In a constant volume calorimeter, `3.5 g` of a gas with molecular weight `28` was burnt in excess oxygen at `298.0 K`. The temperature of the calorimeter was found to increase from `298.0 K to 298.45 K` due to the combustion process. Given that the heat capacity of the calorimeter is `2.5 kJ K^(-1)`, find the numerical value for the enthalpy of combustion of the gas in `kJ mol^(-1)`

Explanation

`T_(i) =298K`
`T_(f)=298.45K`
`k=2.5kJ K^(-1)`
`m=35g`
`M_(m) =28`
heat evolved = `kDeltaT`
`k(T_(f)-T_(i))`
`=2.5 KJ K^(-1)(298.45-298)K`
`=1.125kJ`
`DeltaH_(C)=(1.125)/(3.5)xx28 KJ mol^(-1)`
`DeltaH_(C)=9 KJmol^(-1)`