The Beer-Lambert Law and Quantitative Absorption · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Turning light readings into amounts

Science · Chemistry · ages 18-19
Name ______________________   Date ____________

  1. Which wavelength do you choose for analysis, and why?

    • The peak, where the chemical soaks up most strongly
    • The valley, where readings look tidiest
    • Any wavelength the lamp provides

  2. What do A, l, and c stand for in the Beer-Lambert equation?

    • The colour of the solution
    • Absorbance, path length, and concentration
    • The age of the lamp

  3. A high molar absorptivity means you need a lot of chemical to see any absorbance.

    Circle one:   True   False

  4. Only one hundredth of the light gets through. What is the absorbance?

    • 0
    • 1
    • 2

  5. A solution in a 1 cm tube has absorbance 1. Epsilon is 200. What is the concentration?

    Answer: ______________

  6. Your sample reads above the top standard. What do you do?

    • Extend the line upward and read off it
    • Dilute the sample into range and remeasure
    • Switch to a shorter wavelength instead

  7. Only one thousandth of the light gets through. What is the absorbance?

    Answer: ______________

  8. A student trusts an absorbance of 3 read off an extended line. What is the error?

    • No, the line bends there and stray light intrudes
    • Yes, straight lines extend forever
    • Yes, if the cuvette is clean
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Turning light readings into amounts W1-mt_JGdJxTKxav-s1

  1. The peak, where the chemical soaks up most strongly · Peak readings respond most eagerly to tiny amounts.
  2. Absorbance, path length, and concentration · A, l, and c are the three players in the law.
  3. False · High epsilon means tiny amounts already block much light.
  4. 2 · Each factor of ten in transmitted light adds one absorbance unit.
  5. 0.005 · Flip the law to c equals A over epsilon times l.
  6. Dilute the sample into range and remeasure · Above the top standard the straight line cannot be trusted.
  7. 3 · Each tenfold cut in transmitted light adds one unit.
  8. No, the line bends there and stray light intrudes · High concentration failures are predictable, so respect them.
Worksheet · LightMySky