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Is heat capacity dependant on volume or pressure?

  1. Oct 22, 2012 #1
    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....
  2. jcsd
  3. Oct 22, 2012 #2


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    Staff: Mentor

    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.
  4. Oct 23, 2012 #3


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    Science Advisor

    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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