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Homework Help: Heat needed to change temperature of hydrogen gas

  1. Nov 28, 2006 #1
    A rigid container holds 0.650 of hydrogen gas. How much heat is needed to change the temperature of the gas from 50 K to 100 K?
    All right I know this is easy but for some reason I can't get the right answer what i have been doing is using the equation Q=nC_v(T_f-T_i)
    Hydrogen gas is 1 g/mol
    so n= .65 mol
    C_v= 5/2 R= 20.775
    because hydrogen gas is diatomic?
    (T_f-T_i)= 100-50= 50
    so putting it all together I get 675.188
    which is wrong I made Hydrogen monotomic for the hay of it and got 405 J which is wrong too.
    Please tell me what I am doing wrong......:cry:
     
  2. jcsd
  3. Nov 28, 2006 #2

    OlderDan

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    See the highlights in the quote. A contradiction?
     
  4. Nov 28, 2006 #3
    But i also calculated it for monotomic too....
     
  5. Nov 28, 2006 #4

    OlderDan

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    Did you calculate it for diatomic using the correct mass?
     
  6. Nov 28, 2006 #5
    Oh!
    But When I do that I get
    .65/2 = .325
    .325*20.775*50 = 337.6 which is still wrong
     
  7. Nov 28, 2006 #6
    nevermind monatomic at that temp
     
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