A yellow dye, FD&C; yellow 3, is used in some candy coatings. A 1.50 × 10-5 M so

Question

A yellow dye, FD&C; yellow 3, is used in some candy coatings. A 1.50 × 10-5 M solution of this dye has an absorbance of 0.209 at its max . 2, Calculate the molar absorptivity, e, of the dye at this wavelength, assuming a sample cell with a 1.0 cm pathlength. The yellow dye from one piece of candy is completely extracted into 10.0 mL of water and diluted to 50.0 mL with water. The absorbance of the diluted solution is 0.496 at its b. Calculate the molarity of the dye in the diluted solution. Calculate the number of grams of this dye in the coating of one piece of candy (MM ofdve = 271 g/mol).

Explanation / Answer

Q2

A)

Beer’s Law

A = e*l*C

A = absorbance of sample

e is the molar absorptivity , the typical units are 1/M-cm

l size of cuvette, typically reported in cm

c is the molar concentration, in mol per ltier or M

A = e*L*C

(0.209) = e*1*(1.5*10^-5)

E = 0.209/(1.5*10^-5)

E = 13933.33

b)

diluted:

A = e*l*c

0.496 = 13933.33*1*C

C = 0.496 /13933.33 = 0.0000355

then, dilted --> concentrated

Cconc = 50/10 *0.0000355 = 0.0001775 M

c)

mol = MV = (0.0001775)(10*10^-3) = 0.000001775 mol

mass = mol*MW = 0.000001775*271

mass = 0.0004810 g = 0.481 mg

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