What Is the Change in Enthalpy for Diamond to CO2 at High Temperatures?

[Junkwisch]

Homework Statement

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

Homework 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

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"

 

[Chestermiller]

Homework Statement

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

Homework 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

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"[/QUOTE]

There are several confusing points about this problem statement. I think the statement meant to say "what is the change in enthalpy for the process diamond --> CO2 at the high temperatures of house fires if the change in enthalpy at 298 K and 1 atm is -395.41 kJ/mole. I think you meant to say that the pressure is P = 10^+5 Pa (1 atm), rather than P = 10^-5 Pa (0.000001) atm. You don't need to know the number of moles, because the heat of combustion is for 1 mole. It even says -345.41 kJ/mol.

To do this problem, you need to use Hess' Law, so that you can calculate the change in enthalpy at the higher temperature. Are you familiar with Hess' law? If so, tell us your understanding of it. Also, what is a typical temperature for a house fire. You need to research this so that you can solve the problem. You are also going to need to know the molar heat capacity of C(s) and CO2(g) by researching this on line.

Chet