penehtaCheniistry Questions: 1. If you were given an unknown solution of BTB whi

Question

penehtaCheniistry Questions: 1. If you were given an unknown solution of BTB which also contained MO, as well as the molar absorptivity constants of each, could you determine the concentration of each substance in the solution? (Hint: Look at your graph of absorption spectra) Yes or No? Why? 2. If you pipeted 2.50 mL of stock BTB solution into a 25-mL volumetric flask and diluted it to the mark with distilled water, what would be the molarity of this solution? Us ng Beer's law calculate the absorbance of this solution u(show calculations). 3. Given Beer's law, calculate the following for a solution of methyl orange (MO) containing 3.0 mg Mo/L (-2.83 x 104, MW-32734, b = 2.0 cm) Molar concentration Absorbance: Exp 10 Spectrophotometric Determination of BTB 62

Explanation / Answer

Determining concentration of BTB and MO in a solution

From literature

molar absorptivity for BTB = 33251 M-1.cm-1

molar absorptivity for MO = 20178 M-1.cm-1

Therefore,

absorbance = molar absorptivity x path length x concentration

Path length = 1 cm

so,

For solution 2,

0.393 = 33251[BTB] + 20178[MO]

for colution 3,

0.353 = 33251[BTB] + 20178[MO]

solving the two equations,

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