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Homework Help: Adiabatic Process for an Ideal Gas

  1. Jan 14, 2006 #1
    During the compression stroke of a certain gasoline engine, the pressure increases from 1.00 atm to 20.3 atm. Assume that the process is adiabatic and the gas is ideal with (gamma)= 1.40.

    (a) By what factor does the volume change?
    Vfinal = (ans)*Vinitial
    (b) By what factor does the temperature change (when expressed using an absolute scale)?
    Tfinal =(ans) * Tinitial
    (c) If the compression starts with 0.0160 mole of gas at 27.5°C, find the values of Q, W, and Eint that characterize the process.

    I know the relationship is described by PV^(gamma)=constant but am clueless on how to apply this to get the answers.
  2. jcsd
  3. Jan 15, 2006 #2
    pv ^ gamma = constant means you can write

    Pi Vi ^gamma = Pf Vf^gamma. You need to simply rearrange this equation to get Vi/Vf.

    for part b:

    From PV = nRT, you can write Pi Vi/Ti = Pf Vf /Tf

    Since you already know Pi/Pf and Vi/Vf, rearrange the above to get Ti/Tf.

    For part c.

    If i remember correct for adiabetic process, Q=0. So change in internal energy, dE = dW

    and work done on the system W = -intgration (dW) = -intgration (PdV)
    where P= nRT/V

    Limit of integration is Vi to Vf. You will have to use the given info about mole number and temperature to find vi and vf.
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