Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Ideal gas law and pressure

  1. Jun 3, 2005 #1
    hello all. I'm trying to figure out this problem and it's bugging me because it's soooo simple yet i keep getting the wrong answer. here's the problem:

    If 1.00 mol of carbon dioxide gas at 350 K is confined to a volume of 400 cubic centimeters, find the pressure of the gas using the ideal-gas equation.

    Okay.. I know that the ideal gas equation will look like this if I am solving for pressure:

    p = (nRT)/V

    since I want pressure in pascals, then I will convert volume V to cubic meters, and for R constant I will use R = 8.3145 J/mol K

    so far this is the information I have:

    R = 8.3145 J/mol K
    T = 350 K
    n = 1.00 mol
    V = 4 cubic meters

    When I try and solve for pressure, I get 727.5 pascals. I did this 5 times, and I keet getting the same answer. however the book is telling me I'm wrong. Am I not understanding this correct? could this be one of those times the book is wrong? I hope someone can help!
  2. jcsd
  3. Jun 3, 2005 #2
    Your conversion into cubic metres is incorrect, remember it is cubic:



    Use that value for volume and you should calculate the correct answer, which is 7275187Pa or 7.3MPa.
    Last edited: Jun 3, 2005
  4. Jun 3, 2005 #3
    V = 400 cm^3 = 400 * (10^-2 m)^3 = 400 * 10^-6 m^3 = 0.0004 m^3
    I think this is correct value of the volume and if you put it into ideal gas equation you'll get the right answer (i think).
  5. Jun 3, 2005 #4
    thanks to the both of you for your help. i was able to figure it out.. silly mistake. =) night!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook