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Absorbance and Stray light helppp!

  1. Apr 7, 2005 #1
    Hi, I've a chem assignment in which I've to calculate the stray light, Ps as a percentage of the incident light, Po.

    Given the apparent absorbance A(app) 0.047, concentration of the solution 2.00 x 10pwr-6, cell length of 1cm, activity coefficients = 1.

    I calculated the transmittance to be A = -log T , where T = 0.8974

    T = P + Ps / Po + Ps = 0.8974
    T = P / Po = 0.8974

    I'm stuck after that with 2 unknowns in the equation. Could someone advice me on this?

    Thanks a lot!
  2. jcsd
  3. Apr 7, 2005 #2


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    It would help (yourself) a great deal if you could describe the experiment involved.
  4. Apr 7, 2005 #3
    Okie, this is the question given:

    The apparent absorbance of a solution of a weak acid, HA, was measured at different pH values (you may assume the pH meter was correctly calibrated, that activity coefficients are unity throughout, and that concentrations are reliable. A 1.00cm cell was used. None of the buffers used absorbs at the wavelength used. Results were as follows:

    Concentration, M - 2.00 x 10pwr-6

    Apparent Absorbance:
    0.047 at pH 2,
    0.045 at pH 4,
    0.018 at pH 6,
    0.010 at pH 8,
    0.009 at pH 10

    1) Calculate the stray light, Ps, as a percentage of the incident light, Po, in the spectrophotometer used.

    Thanks again! :smile:
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