1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Basic Kinetic theory: How many molecules are there?

  1. Nov 28, 2015 #1
    1. The problem statement, all variables and given/known data
    A closed vessel contains liquid water at equilibrium with its vapor at 100C and 1 atm. 1 gram of water vapor occupies 1670cm^3. Hvap = 2250Jg^-1. How many molecules are there per cm^3 of vapor?How many vapor molecules strike each cm^2 of liquid surface per second?

    2. Relevant equations
    PV = NKT
    Q = lm

    3. The attempt at a solution
    N = PV/KT = 3.3E26 molecules of vapor
    I used P = 1.013 E5 N m^-2
    V = 16.7m^3
    T = 373
    Not sure how to get how much water there is.
    Answers are: 2E19 molecules cm^-2 ; 3.3E23 impacts per second
     
  2. jcsd
  3. Nov 28, 2015 #2

    phyzguy

    User Avatar
    Science Advisor

    How many water molecules are there in 1 gm of H2O? You are given the volume of 1 gm, so given these two, you should be able to calculate the number of molecules in 1 cm^3.
     
  4. Nov 28, 2015 #3

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    BTW, 1670 cm3 ≠ 16.7 m3. Check your unit conversions again, since 1 m3 ≠ 100 cm3. :frown:
     
  5. Nov 28, 2015 #4
    Wow. Thanks
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Basic Kinetic theory: How many molecules are there?
  1. Basic Kinetics (Replies: 2)

  2. Molecule Kinetics (Replies: 5)

  3. How many gas molecules (Replies: 4)

Loading...