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# Hess' Law/thermochemistry

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1. Use Hess's law and the thermochemical equations given below to calculate the standard enthalpy change for the reaction between C2H4 and F2.

(see attached for formatted remainder)

2. (Hess's Law) Thermochemical tables tell us that the conversion of one mole of diamond to one mole of graphite is accompanied by the release of 1.9 kJ of energy.

(see attached for the rest)

https://brainmass.com/chemistry/energetics-and-thermodynamics/hess-law-thermochemistry-87672

#### Solution Preview

Dear student

Please see all of the work shown for you in the attached Word document.

1. Use Hess's law and the thermochemical equations given below to calculate the standard enthalpy change for the reaction between C2H4 and F2.

C2H4(g) + 6 F2(g)  2 CF4(g) + 4 HF(g) H° = ?

H2(g) + F2(g)  2 HF(g) H° = -537 kJ
C(s) + 2 F2(g)  CF4(g) H° = -680 kJ
2 C(s) + 2 H2(g)  C2H4(g) H° = +52.3 kJ

What we need to do is to add these three equations together in such a way as to generate the reaction between C2H4 and F2. It's not as hard as you think.

Rule 1: We can turn equations around, so long as we change the sign of the enthalpy term.
Rule 2: We can multiple ...

#### Solution Summary

Solution attaches a Word document to show the calculations to find enthalpy changes and reaction conversions in proper formatting.

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