Standard Enthalpy of formation

1. Oct 16, 2006

Juwad

I've google and read, but could anyone tell me how to find out the standard enthalpy of formation for any compound?

thnx

2. Oct 17, 2006

mrjeffy321

For any compound you say? That might be difficult.
Depending on how common the compound is you can often look up the value for its standard enthalpy of formation in a reference table/book somewhere.
Often chemistry text books will have a decent list in the back appendixes.

Pure substances in their elemental state have enthalpies of formation equal to zero. For example, both Hydrogen gas (H2) and Oxygen gas (O2) both have an enthalpy of formation of zero, when they react,
2H2 + O2 --> 2H2O + delta H
There is a change in enthalpy (exothermic in this case). Since water is the only thing in the reaction which does not have an enthalpy of formation of zero it makes it easy to find its value. Similar methods can be employed to find the enthalpy of formation values of other substances if you know the change in enthalpy of other reactions.
For example,
C (graphite) + O2 (g) --> CO2 (g) + delta H = -393.5 kJ
C (diamond) + O2 (g) --> CO2 (g) + delta H = -395.4 kJ
Through some clever manipulation,
C (graphite) --> C (Diamond) + delta H = +1.9 kJ
In this case the graphite allotrope of Carbon has a zero enthalpy of formation (it is the most stable form of Carbon), so from this we can infer that the diamond allotrope must have an enthalpy of formation of +1.9 kJ/mol.

3. Oct 22, 2006

lightarrow

Here there are many:
http://webbook.nist.gov/chemistry/form-ser.html
Insert the formula and select what you need (example: "condensed phase" if it's a liquid or solid, ecc.)

4. May 31, 2011

Sankalp Goyal

I want to know the standard enthalpy and entropy values for the following:

TiN (Titanium Nitride)
TiC (Titanium Carbide)
VC (Vanadium Carbide)
VN (Vanadium Nitride)

5. May 31, 2011

SpectraCat

6. May 31, 2011

Sankalp Goyal

I'm unable to open this web site due to some blocks applied by higher authority.
If possible, could you copy paste the page.

7. Jun 1, 2011

SpectraCat

I will not copy the page, due to potential copyright violation ... however the heat of formation listed on that page was 337 kJ/mol (I assume they meant -337 kJ/mol).

That value, along with values for TiC and VN, can be found in the NIST chemistry webbook.

http://webbook.nist.gov

Vanadium carbide is not there, but I found a value of -24.1 kcal/mol (note the different units) in an 1964 article from Journal of Physical Chemistry. Here is the citation:

"The Free Energies of Formation of the Vanadium, Niobium, and Tantalum Carbides"
Wayne L. Worrell, John Chipman
Journal of Physical Chemistry, volume 68, issue 4
pp 860–866.

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