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Homework Help: Calculating molar specific heat capacity - not a monatomic gas

  1. Jan 20, 2013 #1
    1. Suppose that 25 J of heat is added to one mole of an ideal gas. The gas expands at a constant pressure of 2.62 x 10^4 pascals while changing its volume rom 4.97 x 10^-4 m^3 to 7.02 x 10^-4 m^3. Calculate C_p and express in Joule / (mole * Celsius)

    2. Relevant equations
    Q = C_p*n*(delta T)
    P(Delta V) = nR(Delta T)

    3. Attempt at solution
    25 J = C_p (1 mole) (Delta T)

    Delta T = .64632 Kelvin
    Delta T = -272.35 Celsius

    25 J = C_p (1 mole) ( .272.35 Celsius)

    C_p = -.0918 J / (mole*Celsius)

    4. Question:
    I inputted the answer into the online system as +.0918 J / (mole*celsius)
    However, it is telling me that I am wrong.

    Could there be a negative molar specific heat capacity? That doesn't make too much sense to me because shouldn't the molar specific heat raise the temperature?

    Or did I do some stupid mistake with units/wrong equations?
  2. jcsd
  3. Jan 20, 2013 #2
    Never mind.

    I see that J/mole*C is the same thing as J/mole*Kelvin
    No need for a conversion.
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