Finding Gas Mass Using Heat Exchange at Constant Pressure and Volume

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SUMMARY

The discussion focuses on calculating the mass of an ideal gas given its heat exchange properties. An ideal gas with a molar mass of 28 kg/mole experiences a temperature increase of 14K with 29J of heat added at constant pressure, followed by a cooling process where 20.7J of heat is extracted at constant volume. The relevant equations include the first law of thermodynamics and the internal energy change equation ΔU=(3/2)nRΔT, where R is 8.31 J/(mol·K). The solution involves determining the number of moles (n) and subsequently calculating the mass (m = 28kg*n).

PREREQUISITES
  • Understanding of the first law of thermodynamics
  • Familiarity with ideal gas laws
  • Knowledge of heat capacities at constant pressure and volume
  • Proficiency in using the equation ΔU=(3/2)nRΔT
NEXT STEPS
  • Learn how to apply the first law of thermodynamics in various scenarios
  • Study the derivation and application of heat capacities for ideal gases
  • Explore the relationship between heat transfer and temperature change in gases
  • Investigate the implications of constant pressure vs. constant volume processes
USEFUL FOR

Students in thermodynamics, physics enthusiasts, and professionals working with gas systems who need to understand heat exchange and mass calculations in ideal gases.

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Homework Statement


The temperature of an ideal gas (M=28kg/mole) has increased 14K by adding 29J of heat at a constant pressure. To cool the gas back to the initaial temperature 20.7J of heat is extracted from the gas at a constant volume. Find the mass of the gas.


Homework Equations


ΔU=(3/2)nRΔT
n=number of moles
R=8.31
T=temperature

The Attempt at a Solution


none
 
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1. ΔT = +14K, Q = 29J: can you use the 1st law to determine the number of moles n as a function of CV, the heat capacity at constant volume?

2. ΔT = -14K, Q = -20.9J: can you use the 1st law again to determine CV?
Then you'd have n and of course m = 28kg*n.
 

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