First Law of Thermodynamics and temperature

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Homework Help Overview

The discussion revolves around a problem involving the First Law of Thermodynamics, specifically focusing on the change in internal energy of a gas in a toy balloon as its temperature changes from 20°C to 52.23°C. The balloon's volume and pressure are provided, and participants are tasked with calculating the increase in internal energy, ΔU, using relevant equations and constants.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the appropriate equations for calculating the change in internal energy and question the values used for the number of moles (n) and molecules (N). There are attempts to clarify the use of units and constants in the ideal gas law and the internal energy equation.

Discussion Status

Several participants are exploring different interpretations of the problem, particularly regarding the calculations of n and N. Some guidance has been offered on unit conversions and the application of the ideal gas law, but no consensus has been reached on the final answer.

Contextual Notes

Participants note potential errors in unit conversions, particularly between cubic meters and liters, and the implications of using different constants for the ideal gas law. There is also mention of discrepancies in answers provided by external systems, which may affect the discussion.

  • #31
Why do you not use SI units? And you do not need to evaluate n or N.

PV=nRT. ΔU=5/2 (nR) ΔT. -->

nR=PV/T , ΔU=2.5 PV ΔT/T.

P=101.3 kPa=1.013 e5 Pa. V=4.2 e-3 m3. T=293 K, ΔT=32.23 K.

The result is in joules.
 

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