Calculate ΔH for the following reaction, which describes the production of syn-gas from carbon: H2O(g)+C(s)→CO(g)+H2(g).

Question

Calculate ΔH for the following reaction, which describes the production of syn-gas from carbon:

H₂O(g)+C(s)→CO(g)+H2(g).

 

The following enthalpy changes are known: 

H₂(g)+¹/₂O₂(g)→H₂O(g) ΔH=−242.0 kJ

2CO(g)→2C(s)+O₂(g) ΔH=+221.0 kJ

Answer 1

Rewrite the first and second reactions in reverse and reverse the signs of ΔH: 

H2O(g) -à H2 + 1/2O2   ΔH = +242.0 kj

2C(s) + O2(g) --à 2CO(g)  ΔH = -221.0 kj   

           

Divide the second reaction by 2 to get

C(s) + 1/2O2(g) -à CO(g) ΔH = -110.5 kJ

Add the first equation to the last equation:

H2O(g) + C(s) + 1/2O2(g) à H2(g) + + 1/2 O2(g) + CO(g) and cancel the 1/2O2(g). This gives you the reaction you want.

Add the ΔH values for the first and last separate reactions: ΔHnet = +242 kj – 110.5 kj = 131.5 kj