Question

I am having difficulty with understanding this particular types of problems.

1) Calculate ΔHrxn for the following reaction:

C(s)+H2O(g)→CO(g)+H2(g)

Use the following reactions and given ΔH values:

C(s)+O2(g)→CO2(g), ΔH= -393.5 kJ

2CO(g)+O2(g)→2CO2(g), ΔH= -566.0 kJ

2H2(g)+O2(g)→2H2O(g), ΔH= -483.6 kJ

2) Calculate ΔHrxn for the following reaction:

5C(s)+6H2(g)→C5H12(l)

Use the following reactions and given ΔH values.

C5H12(l)+8O2(g)→5CO2(g)+6H2O(g), ΔH=−3244.8 kJ
C(s)+O2(g)→CO2(g), ΔH=−393.5 kJ
2H2(g)+O2(g)→2H2O(g), ΔH=−483.5 kJ

Answer 1

1)

Lets number the reaction as 0, 1, 2, 3 from top to bottom

required reaction should be written in terms of other reaction

This is Hess Law

required reaction can be written as:

reaction 0 = +1 * (reaction 1) -0.5 * (reaction 2) -0.5 * (reaction 3)

So, deltaHo rxn for required reaction will be:

deltaHo rxn = +1 * deltaHo rxn(reaction 1) -0.5 * deltaHo rxn(reaction 2) -0.5 * deltaHo rxn(reaction 3)

= +1 * (-393.5) -0.5 * (-566.0) -0.5 * (-483.6)

= 131.3 KJ

Answer: 131.3 KJ

Only 1 question at a time please