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Homework Help: Ideal gas mcq

  1. Jun 8, 2012 #1
    1. The problem statement, all variables and given/known data
    A balloon with a constant volume is in 1000C. The fraction of gas flow out of balloon when temperature increased by 20C is nearly equal to
    (consider pressure and the gas in balloon is ideal)

    a. 2/373
    b. 2/375
    c. 2/100
    d. 373/375
    e. 100/102

    2. Relevant equations
    PV=nRT
    P-pressure
    V-volume
    n-number of mols
    R-universal gas constant
    T-temperature

    3. The attempt at a solution
    In these conditions P,n & R is constant
    ∴ V α T
    V1/V2=T1/T2
    V1/V2=375/373

    the amount flow out = 375/373-1 = 2/373

    but the answer given as as 2/375
    the book i get this considered the mass is increasing when temperature increases

    in book that was like

    PV=(m/M)RT
    P,V,M and constant (m-mass of gas, M-molar mass)

    m α 1/T
    m1T1=m2T2
    m1/m2=373/375

    the mass flow out = 1-373/375=2/375

    which is right
     
  2. jcsd
  3. Jun 9, 2012 #2

    ehild

    User Avatar
    Homework Helper

    The volume of the balloon is constant, but n, the amount of gas in it is different. The pressure is the same at both temperature. You have the equations

    PV=n1 R T1
    and
    PV=n2 R T2.

    ehild
     
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