Question

Calculate the ΔHrxn for the following reaction:

CH4 (g) + 2Cl2 (g) --> CH2Cl2 (g) + 2HCl (g)
Use the following reaction and given ΔH's:
CH4 (g) + Cl2 (g) --> CH3Cl (g) + HCl (g), ΔH = -99.60 kJ
CH3Cl (g) + Cl2 (g) --> CH2Cl2 (g) + HCl (g), ΔH = -105.8 kJ

Answer 1

Answer: -205 kJ

Step-by-step explanation:

Since this represents two consecutive processes to yield a particular product, we can see that nothing needs to be done to either equation. They can simply be added together as they are, and things will cancel to yield the desired product.

−99.6 kJ–105.8 kJ=−205 kJ

Answer 2

CH4 (g) + 2Cl2 (g) --> CH2Cl2 (g) + 2HCl (g) ΔH = -205.4