Calculating DeltaE for a Gas Expansion

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SUMMARY

The calculation of DeltaE for a gas expansion process involves the gas absorbing 42J of heat and performing 14J of work on the surroundings. The correct formula used is DeltaH = DeltaE - Q, leading to the equation 42 = DeltaE - 14. This results in DeltaE being calculated as +28J. A common misconception arises with the alternative calculation suggesting DeltaE = 42 + 14, which is incorrect.

PREREQUISITES
  • Understanding of thermodynamic principles, specifically the first law of thermodynamics.
  • Familiarity with the concepts of heat transfer and work in thermodynamic processes.
  • Knowledge of the relationship between DeltaE, DeltaH, and heat (Q).
  • Basic algebra skills for solving equations.
NEXT STEPS
  • Study the first law of thermodynamics in detail.
  • Learn about the differences between internal energy (DeltaE) and enthalpy (DeltaH).
  • Explore examples of gas expansion work calculations in thermodynamics.
  • Review common mistakes in thermodynamic calculations to avoid misconceptions.
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Chemistry students, educators, and anyone studying thermodynamics or preparing for chemistry exams will benefit from this discussion.

liftedrifter
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Homework Statement



Calculate DeltaE of a gas for a process in which the gas absorbs 42J of heat and does 14J of work on the surroundings. (ie the gas expands)

Homework Equations


DeltaH=DeltaE-Q


The Attempt at a Solution


42=deltaE-14

DeltaE=+28J

This is one of the last problems on my chem review and it just seems too easy. If anyone could verify my process that would be great.
 
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liftedrifter said:

The Attempt at a Solution


42=deltaE-14

DeltaE=+28J

This is one of the last problems on my chem review and it just seems too easy. If anyone could verify my process that would be great.

wouldn't then ΔE=42+14 ?
 

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