General chemistry help! Calculate H°f of:?
Please explain how you get the answer. Thank you!!
Use following data:
NO2Cl (g) --> NO2 (g) + 1/2 Cl2 (g) ΔH°rxn= +20.6 kJ/mol
1/2 N2 (g) + O2 (g) --> NO2 (g) ΔH°f = + 33.2 kJ/mol
Calculate H°f of:
1/2 N2 (g) + O2 (g) + 1/2 Cl2 (g) --> NO2Cl (g)
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Answers & Comments
This is an example of using Hess' Law
If you reverse the first reaction you get
NO2(g) + 1/2Cl2(g) ===> NO2Cl(g) ∆H = -20.6 kJ/mol and add this to the second equation...
1/2 N2(g) + O2(g) ===> NO2(g) ∆H = +33.2 kJ/mol
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NO2(g) + 1/2Cl2(g) + 1/2 N2(g) + O2(g) ===> NO2Cl(g) + NO2(g)
Cancel those that appear on both sides to get
1/2Cl2(g) + 1/2 N2(g) + O2 ==> NO2Cl(g) and to get ∆Hrxn
you add the -20.6 kJ/mole and the 33.2 kJ/mole to get 12.6 kJ/mole <==Answer