1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Finding mass based on amu and % abundance

  1. Sep 24, 2008 #1
    1. The problem statement, all variables and given/known data

    Oxygen has 3 isotopes. Oxygen-16 has the amu of 15.995 and its natural percent abundance is 99.759. Oxygen-17 has a mass of 16.995 amu and its natural percent abundance is 0.037. Oxygen-18 has a mass of 17.999 amu and its natural percent abundance is 0.204. What is the average atomic mass of oxygen?

    2. Relevant equations

    I think I forgot these...

    3. The attempt at a solution

    I couldn't remember what the process is supposed to look like to figure this sort of problem out, so I tried to multiply the mass by the percent abundance, but the answers made very little sense. If somebody could help me figure out where I messed up, PLEASE RESPOND!
  2. jcsd
  3. Sep 24, 2008 #2


    User Avatar
    Homework Helper
    Education Advisor
    Gold Member

    The average atomic mass of an element is much like a simple mixture problem that you learn in first year Algebra such that you can resort directly to percentage contributions formula.

    AverageAMU = 0.99759*16 + 0.00037*17 + 0.00204*18
  4. Sep 24, 2008 #3
    Thank you so much!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook