Is heat capacity dependant on volume or pressure?

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SUMMARY

The discussion clarifies that molar heat capacity can refer to either constant pressure (C_p) or constant volume (C_v), with the distinction being particularly significant for gases. For ideal gases, the relationship is defined by the equation C_p = C_v + R, where R is the gas constant. However, for liquids and solids, the difference between C_p and C_v is minimal and generally negligible in most chemical contexts, except in high-pressure scenarios.

PREREQUISITES
  • Understanding of thermodynamic principles, specifically heat capacity.
  • Familiarity with ideal gas laws and equations.
  • Knowledge of the differences between constant pressure and constant volume conditions.
  • Basic chemistry concepts related to states of matter (gases, liquids, solids).
NEXT STEPS
  • Research the specific heat capacities of various liquids and solids under different conditions.
  • Study the implications of high-pressure reactions on heat capacity.
  • Learn about the applications of heat capacity in thermodynamic cycles.
  • Explore the differences in heat capacity measurements for real gases versus ideal gases.
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Chemists, chemical engineers, and students studying thermodynamics who seek to understand the nuances of heat capacity in different states of matter.

Nikitin
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hi. When you're given molar heat capacity for a substance, is it when under constant pressure or when under constant volume? Like water's heat a capacity when gaseous is 75kJ/mol - is this under constant volume?

For an ideal gas, the formula for heat capacity under constant pressure is: Cp = Cv + R. Is there something similar with liquids?

Please explain this to me, as I'm very confused about all this stuff...
 
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Yes, there are separate constant pressure and constant volume specific heats for all substances, but only for gases (and only when their behavior is close to ideal) the dependence is nice and clear.
 
For liquids and solids the difference between C_p and C_V is small and seldomly matters in chemistry, maybe with the exception of high pressure reactions.
 

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