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 order of a reaction

  1. May 20, 2013 #1
    I've attached a screenshot of the internet page where the homework questions are, which shows the problem and my answers (It says I got A right, but B and C are wrong).

    So I did this a few times with other tables and got the right answers, but this one is weird and the website isn't recognizing my answer.

    So what I did was take the 3rd value of A, divided it by the 1st value of A and got 2 as the answer. I used those rows because A changes in those rows while B stays the same.

    Then used the same rows to divide the 3rd row of the rate by the 1st row of the rate, and got 2 as my answer. 2 divided by 2 is 1, so the order is 1 for A. I got that one right.

    Then I did the same thing with B. I divided the second row of B by the 1st row of B to get 1.666666667 as my answer. Then divided the second row of the rate by the 1st row of the rate to get 1. 1 divided by 1.66666667 = 0.6. It says that's wrong.

    And the total order is 0.6 + 1, which is 1.6, which it says is wrong. The problem lies with the answer I got for B, but I don't know what I did wrong.
    Maybe it has something to do with sig figs, but my calculator gives me an exact answer of 0.6.

    Attached Files:

  2. jcsd
  3. May 20, 2013 #2


    User Avatar
    2017 Award

    Staff: Mentor

    In general, it does not work like that - the division gives the correct result only in some special cases, or if the order is 1.

    As you can see in row 1 and 2, the reaction rate does not depend on B at all. What does this tell you about the reaction order?
  4. May 20, 2013 #3
    Ohhhhh, of course. I didn't think about that. So that means the rate of the reaction is independent of the concentration of B, which means B is zero order. Thank you very much.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted