Question

Given that:
i. `C(s) + O_(2)(g) rarr CO_(2)(g) , DeltaH =- 94.05 kcal`
ii. `H_(2)(g) +(1)/(2) O_(2)(g) rarr H_(2)O(l), DeltaH =- 68.32 kcal`
iii.`C_(2)H_(2)(g) +(5)/(2) O_(2)(g) rarr 2CO_(2)(g) +H_(2)O(l), DeltaH =- 310.62 kcal`
The heat of formation fo acetylene is
A. `-1802kJ`
B. `+1802kJ`
C. `-800kJ`
D. `+228kJ`

Answer 1

Correct Answer - D
Required equation is ltBrgt `2C(s)+H_(2)(g)toC_(2)H_(2)(g)`
Eq. (i)+eq.(ii)-eq.(iii) gives
`DeltaH=(-787)+(-286)-(-1301)`
`=+228kJ`