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A solution contains 0.00520M of a first compound with an extinction coefficient of 52.4cm−1M−1. A second compound with an extinction coefficient of 5.26cm−1M−1 is added to the solution. The absorbance through a path length of 1.00cm is 0.792 for the solution containing both compounds. What is the concentration of the second compound in the solution?

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Final answer:

To calculate the concentration of the second compound, the Beer-Lambert Law is applied using the given total absorbance, path length, and the extinction coefficients of both compounds present in the solution. The concentration of the second compound is determined to be 0.09884340M.

Step-by-step explanation:

The concentration of the second compound in the solution is calculated using the Beer-Lambert law, which relates absorbance (A), molar absorptivity (ε), concentration (c), and path length (l). Given the total absorbance of the solution and the extinction coefficients for both compounds, we can set up an equation to solve for the unknown concentration of the second compound:

A = (ε1·c1 + ε2·c2)·l

Given values:


  • Total absorbance (A) = 0.792

  • Extinction coefficient of first compound (ε1) = 52.4 cm-1M-1

  • Concentration of the first compound (c1) = 0.00520M

  • Path length (l) = 1.00 cm (as per the standard cuvette size)

  • Extinction coefficient of the second compound (ε2) = 5.26 cm-1M-1

Plugging in all the known values into the Beer-Lambert law equation allows us to solve for the concentration of the second compound (c2):

0.792 = (52.4·0.00520 + 5.26·c2)·1.00

Solving for c2, we find that:

0.792 = (0.27208 + 5.26·c2)

c2 = (0.792 - 0.27208) / 5.26

c2 = 0.09884340M

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