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Enthalpy of Formation

by Physics197
Tags: enthalpy, formation
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Jan23-10, 03:11 PM
P: 74
1. The problem statement, all variables and given/known data

Using the enthalpies of formation given below, calculate ΔHrxn in kJ, for the following reaction.

3NO2(g)+1H2O(l) -> 2HNO3(g)+1NO(g)

NO2 (g): 33.10 kJ/mol
H2O (l): -285.83 kJ/mol
HNO3 (l): -174.10 kJ/mol
NO (g): 90.29 kJ/mol

2. Relevant equations

dHrxn = dHproducts - dHreactants

3. The attempt at a solution

Is this possible to do since the equation says HNO3 is a gas, but they give the enthalpy of formation for HNO3 as a liquid.
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Jan26-10, 09:03 PM
P: 271
its possible but you need to use another enthalpy term that accounts for the latent heat which is from the phase transfer of liquid to gas
Jan27-10, 03:24 PM
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P: 3,724
That would be the Hvap of HNO3.

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