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: Atom economy question

  1. May 14, 2012 #1

    To work out the answer to this question, do I just find the total Mr of the products and divide it by the total Mr of the reactants (and then multiply by 100, and pick the biggest percentage?)

  2. jcsd
  3. May 14, 2012 #2
    If you did that, you would get %100 every time. Otherwise, you would be violating conservation of mass.

    If you want to know the effency of producing Oxygen from your reactants, which product mass do you want to use in your equation?
  4. May 14, 2012 #3
    If you do it for A, you get 118 %... (so I am doing something wrong?)

    Mr of (NaNO2 + (1/2)O2) = 101
    Mr of (NaNO3) = 85

    (101/85)*100 = 118.8%

    For A, wouldn't we use both products, since both products contain Oxygen?
  5. May 14, 2012 #4
    Mr of (NaNO2 + (1/2)O2) = 101

    You did this one wrong. You forgot to take 1/2 the mass of o2

    For A, wouldn't we use both products, since both products contain Oxygen?

    No. We're only concerned with O2 as Oxygen gas. If the Oxygen is still in a compound, you haven't made oxygen.
  6. May 14, 2012 #5

    Oh, I always thought that when calculating the Mr, you do not consider the coefficients. Thanks for clearing that up..

    So would this be a correct calculation (for A):

    Mr of (1/2)O2 = 16
    Mr of NaNO3 = 85

    so 16/85 x 100 = 18.8%
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook