Question

The gasification of coal is a method of producing methane by the following reaction. C(s) + 2H2(g) → CH4(g) ∆H=?

Answer 1

Using Hess' Law, we can calculate the heat of reaction of the gasification of coal. Multiplying the second reaction by 2 and reversing the third reaction:

C(s) + O2(g) → CO2(g) ∆H=-394 kj 
2H2(s) + O2(g) → H2O(l) ∆H=-572kj 
CO2(g) + 2H2O(l) → CH4(g) + 2O2(g) ∆H=891kj 

Adding the three reaction would result to
C(s) + 2H2(g) → CH4(g) ∆H = -394 + -572 + 891 = -75 kJ

The answer is
(B) -75 kJ 

Answer 2

Hello there.

The gasification of coal is a method of producing methane by the following reaction. C(s) + 2H2(g) → CH4(g) ∆H=? 
Find ∆H by using the enthalpy changes in the following combustion reactions: 
C(s) + O2(g) → CO2(g) ∆H=-394 kj 
H2(s) + ½ O2(g) → H2O(l) ∆H=-286kj 
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) ∆H=-891kj 

(B) -75 kJ