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Homework Help: Give 70J as heat to a diatomic gas

  1. Dec 12, 2004 #1
    Hi guys, I'm trying to interpret this problem but am having difficulties.

    "We give 70J as heat to a diatomic gas, which then expands at constant pressure. The gas molecules rotate but do not oscillate. By how much does the internal energy of the gas increase"

    Does "The gas molecules rotate but do not oscillate" mean the volume does not change?

    I'm assuming I'd use deltaU = deltaQ - deltaW, with deltaW being p*deltaV since constant pressure. If the deltaV were 0 then deltaQ=70J-0 therefore yielding the answer of 70J which does not feel very comfortable, being the same.
  2. jcsd
  3. Dec 12, 2004 #2


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    You can view the molecules as rigid rotors - they have two rotational degrees of freedom but the two atoms comprising a molecule are constrained to a fixed separation from each other.

    HINT: Think equipartition of energy!
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