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i safari File Edit View History Bookmarks Window Help access3.lon.capa.illinois.edu 0 DNA & R Chr11: 2,16 Chegg de Broglie Prelab 3 The 1.396x10-5 M You are correct Your receipt no. is 163-9552Previous Tries Content e Master 5, what is the concentration of the solution #2 in terms of molarity? 8.568x10-6 M View You are correct. Your receipt no. is 163-3126 31 6. You measure the absorbance of each solution (at Amax524 nm) and obtain the following results: Solution Absorbance Stock solution Solution #1 Solution #2 2.95 0.515 0.315 100% Determine the average epsilon for FD&C; Red 40. 34 M1cm-1 Submit Answer Incorrect. Tries 1/99 Previous Tries 35 7. You are given an unknown solution of FD&C; Red 40. You measurethe aborbance and find it to be 0.671 at 524 nm. 36 Determine the concentration of the unknown solution in terms of molarity Submit Answer Tries 0/99

Explanation / Answer

6. If molarity of solution #1 = 1.396 x 10^-5 M

molarity of solution #2 = 8.568 x 10^-6 M

using absorbances,

absorbance for solution #1 = 0.515

absorbance for solution #2 = 0.315

the average epsilon (molar absorptivity) = (0.315 - 0.515)/(8.568 x 10^-6 - 1.396 x 10^-5)

                                                                = 37092 M-1.cm-1

7. absorbance of unknown solution = 0.671

using,

concentration = absorbance/molar absorptivity x path length

where,

path length = 1 cm

we get,

concentration of the unknown solution = 0.671/37092 = 1.81 x 10^-5 M

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