Determine enthalpy change for,
`C_(3)H_(8(g))+H_(2(g))rarr C_(2)H_(6(g))+CH_(4(g))`
at `25^(@)C` using heat of combustion values under standard condition.
`{:(Compounds,H_(2(g)),CH_(4(g)),C_(2)H_(6(g)),C_((Graph ite))),(DeltaH^(@)i n kJ//mol,-285.8,-890.0,-1560.0,-393.5):}`
The standard heat of formation of `C_(3)H_(8(g))` is `-103.8 kJ mol^(-1)`.

Explanation

`(H_(2)+(1)/(2)O_(2) rarrH_(2)O xx 5)`
`-(CH_(4)+2O_(2) rarr CO_(2) +2H_(2)O)`
`-(C_(2)H_(6)+(7)/(2)O_(2) rarr 2CO_(2)+3H_(2)O)`
`-(C _(2)H_(6)+(7)/(2)O_(2) rarr 2CO_(2)+3H_(2)O)`
`(C +O_(2) rarr CO_(2)) xx 3`
`-(3C +4H_(2) rarr C_(3)H_(8))`
`ulbar(C_(3)H_(8)rarrC_(2)H_(6)+CH_(4)("desired equation"))`
Giving similar treatment to values of `DeltaH`,we have
`(-258.8 xx 5) - (-890) -(-1560) +(-393.5 xx3)`
`-(-103.8) =- 1429 +890 +1560 - 1180.57 +103.8`
`= 2553.8 - 2609.5 =- 55.7 kJ`