# Calculating the change in Enthalpy

1. May 3, 2014

### Junkwisch

1. The problem statement, all variables and given/known data

A house fire generates sufficient temperatures to ignite diamond and cause it to burn into CO2. What is the change in enthalpy of the process “diamond to CO2” with the system at T = 298 K and P = 10^-5 Pa? The enthalpy of combustion of diamond is –395.41 kJ/Mol

2. Relevant equations

H=U+PV
F=U-TS
G=U-TS-PV=H-TS

Hess's Law,

where H is enthalpy
F is Helmholtz free energy

3. The attempt at a solution

I was told to find the change in enthalpy when diamond is convert into CO2

C(s,diamond)--> CO2 = -395.41kJ,Mol

since Enthalpy of combustion = released energy x number of moles

thereby released energy/enthalpy = Enthalpy of combustion / number of moles

But I do not know the number of moles, this were not stated in the question as well

"I have yet to be taught on this topic, and it is unlikely that I will be. I was told to answer this while giving this link http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/Thermodynamic_Cycles/Hess's_Law" [Broken]

Last edited by a moderator: May 6, 2017
2. May 7, 2014

### Staff: Mentor

Last edited by a moderator: May 6, 2017
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