Calculate the standard heat of formation of propane, if its heat of combustion is-2220.2 kJ `"mol"^(-1)` , the heats of formation of `CO_(2(g))` and `H_2O_((l))` are - 393.5 and -285.8 kJ `"mol"^(-1)` respectively.

Explanation

Given : `C_3H_8+5O_2 to 3CO_2 + 4H_2O`
`DeltaH_C^0=-2220.2 "kJ mol"^(-1)`….(1)
`C+O_2 to CO_2`
`DeltaH_f^0=-393.5 "kJ mol"^(-1)` …(2)
`H_2+1//2 O_2 to H_2O`
`DeltaH_f^0=-285.8 "kJ mol"^(-1)` …(3)
`3C+4H_2 to C_3H_8`
`DeltaH_C^0`=?
`(2)xx3 rArr 3C+3O_2 to 4H_2O`
`DeltaH_f^0`=-1143.2 kJ ...(5)
(4) + (5) -(1)
`rArr 3C+3O_2+4H_2+2O_2 +3CO_2+4H_2O to 3CO_2 +4H_2O +C_3H_8 +5O_2`
`DeltaH_f^@`=-1180.5 -1143.2 -(-2220.2 ) kJ
`3C+4H_2 to C_3H_8`
`DeltaH_f^0=-103.5 "kJ mol"^(-1)`
Standard heat of formation of propane is `DeltaH_f^0(C_3H_8)=-103.5 "kJ mol"^(-1)`