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Homework Help: Gas laws

  1. Apr 4, 2007 #1
    If there are 6.25 L of Hydrogen gas at a pressure of 1.95 ATM and a temperature of 243 K, how many grams of hydrogen are there?

    I know that the equation for the ideal gas law is:
    pV = nRT
    p = pressure
    V = volume
    n = number of moles
    R = the gas constant, 0.0821 L atm mol-1 K-1
    T = temperature

    but I don't know how to fill in n, the number of moles.
    this is my unfinished equation:
    (1.95 atm) (6.25 L) = (n) (0.00821 atm mol-1 K-1) (243 K)

    help, please!
  2. jcsd
  3. Apr 4, 2007 #2

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    You know PV = nRT, and you are given P, V, R, and T. You even have R in the correct units. Just solve it!
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