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Homework Help: Molar Heat Problem

  1. Feb 6, 2007 #1
    1. The problem statement, all variables and given/known data
    If a heater supplies 1.8 x 10^6 J/h to a room 6.5 m x 4.6 m x 3.0 m containing air at 20 oC and 1.0 atm, by how much will the temperature rise in one hour, assuming no heat losses to the outside?

    2. Relevant equations
    Q = n*Cv*(Tfinal - Tinitial)
    PV = nRT -> n = (PV / RT)
    Q = Delta U

    3. The attempt at a solution
    - It is isochoric. Meaning: volume doesn't change so there is no work involving volume.

    (1.8 x 10^6 J / h) (1 calorie / 4.186 J) = 430004.7778 calories

    PV = nRT -> n = (PV / RT)

    P = 1 atm = 1.013x10^5 N/m^2
    V = 6.5 m * 4.6 m * 3.0 m = 89.7 m^3
    R = 8.315 (?)
    T = 20 + 273.15 = 293.15 K
    n ~ 3727.775 mol

    ---
    Q = n * Cv * (Tfinal - Tinitial)

    n ~ 3727.775 mol
    Cv = 2.98 (cal / mol * K)
    T = (Tfinal - 20 oC)
    Q = Delta U
    Delta U = 430004.7778 calories ?
    Q = 430004.7778 calories ?

    I'm not sure how to tie this problem together to solve for Tfinal. I'm not sure if I have this correct.

    The answer is 22 oC / hour. I cannot get this.
     
    Last edited: Feb 6, 2007
  2. jcsd
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