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Order Rate

  1. Mar 12, 2010 #1
    1. The problem statement, all variables and given/known data

    Calculate Order of Each Reactants
    I am doing a lab on the reaction rates for k[BrO3-]y[I-]x[H+]z However when I do my calculations based on my data, i get different orders! The teacher said that will happen but how am I supposed to know which is the right one?


    3. The attempt at a solution
    log(5.3E-7/7.6E-7)/log(0.0017/0.0033)=0.5-I
    log(5.3E-7/1.2E-6)/log(0.0067/0.0133)=1- BrO3-
    log(5.3E-7/2.8E-6)/log(0.0067/0.0200)=1.5- BrO3-
    log(1.2E-6/2.8E-6)/log(0.0133/0.0200)=2- BrO3-
    log(5.3E-7/2.02E-6)/log(0.0167/0.0333)=2- H
    log(5.3E-7/3.8E-6)/log(0.0167/0.0500)=2-H
    log(2.02E-6/3.4E-6)/log(0.0333/0.0500)= 1 H
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 13, 2010 #2
    I can't tell from your math what your numbers actually mean, since none of them have units or descriptions.

    Can you list your data for each set of measurements?
     
  4. Mar 13, 2010 #3
    Exp #---- Time of reaction (s) - -- Reaction rate (M/s)---- Initial Concentrations (M)
    Trial 1---Trial 2---Trial 3-- -Average --- [I-] --- [BrO3-] ------[H+]
    1- 26.27- -- 27.2 --- 24.5 ---25.99 ---5.3E-7---------0.0017---0.0067 ---0.0167

    3 -9.59 --- 7.79 --- 5.68--- 7.69--- 1.8E-6------- 0.0050--- 0.0067--- 0.0167
    4- 12.87 --- 11.8--- 10.75--- 11.8---1.2E-6 -------0.0017---0.0133 ---0.0167
    5 -4.49---4.40--- 5.90--- 4.90 ---2.8E-6-------- 0.0017--- 0.0200--- 0.0167
    6- 6.21---7.56--- 6.72 --- 6.83---2.02E-6---------0.0017---0.0067---0.0333
    7- 4.39---4.14 --- 3.74--- 4.09--- 3.4E-6--- ---------0.0017--- 0.0067--- 0.0500


    for BrO3 i used experiments 1,4,5
    for I i used experiment 1 and 3
    and for H i used experiments 1,6 , 7

    Calculations

    log(5.3E-7/7.6E-7)/log(0.0017/0.0033)=1-I
    log(5.3E-7/1.2E-6)/log(0.0067/0.0133)=1- BrO3-
    log(5.3E-7/2.8E-6)/log(0.0067/0.0200)=1.5- BrO3-
    log(1.2E-6/2.8E-6)/log(0.0133/0.0200)=2- BrO3-
    log(5.3E-7/2.02E-6)/log(0.0167/0.0333)=2- H
    log(5.3E-7/3.8E-6)/log(0.0167/0.0500)=2-H
    log(2.02E-6/3.4E-6)/log(0.0333/0.0500)= 1 H
     
  5. Mar 13, 2010 #4
    Where does the 7.6e-7 come from?


    Since you have 3 points for both of these, that's the minimum needed for linear regression.

    Try graphing log[x] vs log(rate) and find the best straight line to fit the data.
     
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