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Homework Help: The final temperature of a gas?

  1. Oct 15, 2011 #1
    1. The problem statement, all variables and given/known data
    Starting with 2.50 mol of N2 gas (assumed to be ideal) in a cylinder at 1.00 atm and 20C, a chemist first heats the gas at constant volume, adding 1.52x10^4J of heat, then continues heating and allows the gas to expand at constant pressure to twice its original volume. Calculate the final temperature of the gas.

    2. Relevant equations

    3. The attempt at a solution
    The first part suggests that the system is in a constant volume. Thus:

    I solve for Tf and I get 312.5C.

    Now the next part suggests the system is at a constant pressure and the volume doubles.
    So I use PV=nRT where n, R and P are constant.

    I solve for and I get 625C. However the answer in the back is 899C. What am I doing wrong?

  2. jcsd
  3. Oct 16, 2011 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    For this equation, T must be expressed as an absolute temperature, not in degrees C.
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