Do enthropy and enthelpy changes depend on pressure?

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SUMMARY

The discussion focuses on calculating the entropy and enthalpy changes for the reaction Al + 1/2 N2 -> AlN at 298 K under varying pressures of 1 atm and 10 atm. The entropy values provided are 6.77 cal/mol-K for aluminum, 45.77 cal/mol-K for nitrogen, and 4.82 cal/mol-K for aluminum nitride. The enthalpy change of formation for AlN is -76,470 cal/mol. It is established that entropy and enthalpy changes depend on pressure, particularly for gases, while changes for solids can generally be neglected.

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  • Understanding of thermodynamic concepts, specifically entropy and enthalpy.
  • Familiarity with the ideal gas law and its implications on gas behavior.
  • Knowledge of standard conditions for thermodynamic calculations (298 K and 1 atm).
  • Basic skills in calculating changes in free energy and thermodynamic properties.
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  • Research the P-V-T behavior of gases to understand how pressure affects thermodynamic properties.
  • Learn about the Gibbs free energy and its relationship to pressure changes in gas reactions.
  • Study the impact of pressure on the entropy of gases versus solids in thermodynamic processes.
  • Explore the concept of ideal gas behavior and its simplifications in thermodynamic calculations.
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Chemistry students, thermodynamics enthusiasts, and professionals involved in chemical engineering or materials science who are interested in understanding the effects of pressure on thermodynamic properties.

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Homework Statement


I have a homework which include this question: Al+1/2 N2-> AlN in this reaction find enthropy and enthalpy changes at 298 K and 1 atm. and repeat these at 298 K and 10 atm.

entropy changes at 298 K
aluminum 6.77 cal/mol-K
Nitrogen 45.77
Aluminum nitride 4.82

enthalpy change of formation of AlN is -76,470 cal/mol


The Attempt at a Solution



i found them at 1 atm but i could not find at 10 atm. are the answers same or do they depend on pressure, if they depend, how can i calculate them?
 
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atomalptunga said:
i found them at 1 atm but i could not find at 10 atm. are the answers same or do they depend on pressure, if they depend, how can i calculate them?
How did you get your values for 1 atm? Did you use the pressure there?
 
The entropy and the enthalpy of the N2 and the AlN (if it is a gas) are functions of pressure. The changes for a solid with pressure can usually be neglected. You can get the change in free energy with respect to pressure of a gas pretty easily if you know the P-V-T behavior of the gas, and you can also do the same for the change in enthalpy. The change in entropy then follows from these. Is AlN a solid or a gas at 1 atm and 298? Of course, if you are willing to assume ideal gas behavior, it's much simpler, because the change in enthalpy is zero, and the change in entropy is R times the natural log of the pressure ratio.
 
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