WBJEE 2014 Chemistry Solved Paper

i) C + O2 → CO2 ; ΔH° = –x kJ
ii) 2CO + O2 → 2CO2 ; ΔH = –y kJ
Eq (i) × 2
2C + 2O2 → 2CO2 ΔH° = – 2 x kJ
Writing eq. (ii) in never e order
2C)2 → 2CO + O2 , ΔH° = y KJ
––––––––––––––––––––––––
adding, 2C + O2 → 2CO, ΔH = (y – 2x) kJ
For 2 mol CO, ΔH = (y – 2x) kJ
∴ For 1 mol CO, ΔHf = (

y−2x

2

) KJ
∴ Enthalpy of formation, ΔH°f =

y−2x

2