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Ideal gas law problem

  1. Jan 5, 2015 #1
    does anyone know how to do this question. it feels like theres a part of the question missing as i dont know how to complete the equation

    The pressure of a fixed mass of gas in a sealed sphere is measured to be 1.02 x 10^5 Pa at a temperature of 253K. Assuming the volume of the sphere doesnt change calculate the pressure within the sphere if the temperature is increased to 281K
    (universal gas constant R =8314 J/K/mol

    because it's a fixed mass of gas do i ignore n? when doing the equation




    2. Relevant equations
    PV=nRT

    3. The attempt at a solution
    (1.02 x 10^5) V = n (8314)(253)
    1.02 x 10^5 V = 2103442n
     
  2. jcsd
  3. Jan 5, 2015 #2

    Bystander

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    What equation are you trying to complete?
     
  4. Jan 5, 2015 #3
    the first part first of all,but there are two unknown variables so i'm not sure what to do
     
  5. Jan 5, 2015 #4
    i know i need to find the volume of the sphere for the first part but iam unsure of how to get a number for n
     
  6. Jan 5, 2015 #5

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    How are you going to use the volume of the sphere once you get it?
     
  7. Jan 5, 2015 #6
    when i have the volume i will use it to find the pressure like so

    P = (n(8314)(281)) / V
     
  8. Jan 5, 2015 #7

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    So, what all has changed besides temperature and pressure?
     
  9. Jan 5, 2015 #8
    nothing
     
  10. Jan 5, 2015 #9

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    Correct.
    Just because the equation uses two variables, does not mean you have to find values for both if they're both constant, and you're interested in solving for the value of some other variable.
     
  11. Jan 5, 2015 #10
    Thank you so much
    :)
     
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