Calculate the heat capacity at constant volume and constant pressure.

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Discussion Overview

The discussion revolves around calculating the molar heat capacities at constant volume and constant pressure for a gas, given specific parameters such as the amount of heat added, the number of moles, and the change in temperature. The context is a homework problem that lacks clarity regarding whether the temperature change occurs at constant volume or constant pressure.

Discussion Character

  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about solving the problem without knowing if the temperature change occurs at constant volume or constant pressure.
  • Another participant requests the exact wording of the question, suggesting that the necessary information might be present but overlooked.
  • A later post clarifies the question, stating the specific energy supplied, the number of moles, and the temperature increase.
  • Some participants agree that the question is unclear, indicating a shared concern about the ambiguity in the problem statement.
  • One participant shares a negative experience with their professor, who seemed unable to clarify the question's assumptions, leading to frustration about potential exam implications.

Areas of Agreement / Disagreement

Participants generally agree that the question is unclear, and there is no consensus on how to approach the problem due to the ambiguity regarding constant volume and constant pressure assumptions.

Contextual Notes

The discussion highlights limitations in the problem statement, particularly the lack of clarity on whether the temperature change occurs under constant volume or constant pressure conditions, which affects the ability to calculate the heat capacities accurately.

LogicX
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Homework Statement



I am given the amount of moles of gas, how many joules of heat I put into the system, and a positive change in temperature. Then it says "calculate the molar heat capacities at constant volume and constant pressure of the gas."

Homework Equations



q=CT, C(constant pressure)-C(constant volume)=nR, U= q+w, H=U+PV

The Attempt at a Solution



I just don't know how to do this problem without knowing whether the temperature change occurs at constant volume or constant pressure. If I knew either of those the problem would be easy.

I have q and delta(T), so I should be able to calculate a heat capacity. But I don't know which one it would be.
 
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Can you give exact wording of the question? Perhaps the information is there, just hidden?
 
"When 178 J of energy is supplied as heat to 1.9 mol of gas molecules, the temperature of the sample increases by 2.55 K. Calculate the molar heat capacities at constant volume and constant pressure of the gas."
 
Nah, you are right - question is unclear.
 
Borek said:
Nah, you are right - question is unclear.

Ok thanks, I'll go talk to my professor tomorrow.
 
Well my professor is a senile old man so I tried to ask him today, but he seemed to have a mental block against admitting he wrote the question wrong so at first he tried to tell me I can assume the pressure is constant, then that I can assume that the volume is constant.

I guess I just have to hope that he doesn't pull this **** on the exam because he would probably just arbitrarily pick one that he wanted us to assume was constant and if I confronted him about it get the same talking in circles answer that I got just now.

I hate college sometimes.
 

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