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: Beer's law

  1. Oct 27, 2008 #1
    1. The problem statement, all variables and given/known data
    IF I=15.0 mW (s=0.29), I0=75.6 mW (s=0.64), b=1.00 (s=0.02) and c= 2.32*10^-3 (s=0.05*10^-3), what is the molar absorptivity for the absorbing species? Calculate the result, the absolute standard deviation, and the relative standard deviation in parts per thousand of the result.

    2. Relevant equations


    Sx/x =SQRT((Sp/P)2+(Sq/q)2+(Sr/R)2


    RSD = S/x *10^x

    3. The attempt at a solution

    (75.6/15) = 5.04

    log(75.6/15.0)= 0.702


    Standard Deviation:

    STD of log(I0/I) = 0.434((SQRT(((0.64/75.6)^2)+((0.29/15.0)^2))/5.04))=0.013

    STD of bc = SQRT(((0.02/1.0)^2)+((0.05*10^-3/2.32*10^-3)^2)) = 0.03

    STD of a = SQRT(((0.013/0.702)^2)+((0.03/(2.32*10^-3))^2) = 12.67

    I am not sure about the standard deviation of the molar absorptivity (a) or what value to use to calculate the relative standard deviation I know it is the standard deviation divided by the average, but value is the average.
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted