Enthalpy of A Reaction Using Hess' Law

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Calculating Entropy using Hess's law

Find the enthalpy of the following reactions:

NOg + ½ o2 NO2
Cgraphite C diamond

5C(s) +6H2(g) C5H12

1. There are 2 ways to solve these problems. One can solve them using Hess's law or one can solve them using the following formula:
∑ { (ΔH products) x (mol products)} - ∑{ ( ΔH reactants) x ( mol reactants)}

I will solve them using hess's law and I will use the above formula to check my answers for some of the problems.

Formation of NO2

Add ΔH of each component reaction. Don't forget to reverse the reaction if necessary to obtain the desired product. If one reverses the reaction, one needs to assign the opposite sign to the ΔH value.

Write the equation for the formation of NO as follows:
½ N2(g) + ½ o2(g) NO(g) Δ H = 90.29 kj

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