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Homework Help: Question about Ideal Gas Law

  1. Jul 3, 2013 #1
    1. The problem statement, all variables and given/known data
    A sample containing only NO2 and SO2 has a total pressure of 120 torr. Measurements show that the partial pressure of NO2 is 43 torr. If the vessel has a volume of 800.0 ml and the temperature is 22.0°C, how many moles of each gas are present?

    2. Relevant equations

    PV = nRT

    3. The attempt at a solution
    I tried to solve it using the equation above by solving for n for each gas (using their given pressure).
    For the n of NO2, I had the answer 3.1 x 10-3 (using n = PV/RT).
    But the book provides a different answer for it which is 1.9 x 10-3.

    My question is I would like to know how my answer turned to be incorrect. I don't know any other possible methods of solving this than the ideal gas law.
    Thank you.
  2. jcsd
  3. Jul 4, 2013 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    I suspect you have either an arithmetic mistake and/or a mistake in units.

    Please post the details of your calculations.
  4. Jul 4, 2013 #3


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    Staff: Mentor

    Book answer is correct.
  5. Jul 4, 2013 #4
    Okay guys, I got it. I had an error in manipulating the equations. Thank you PF for helping me resolve the problem!
  6. Jul 5, 2013 #5
    I'm curious as to how you arrived at the correct answer. Could you show your work?
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