Question

Name Lab Section: 1 2 345 6 789 Pre-lab: Concentration of Riboflavin 1. The following absorbance spectrum is recorded for a dye. Which is the most likely color of this dve? a Blue-green b. Colorless c. Red d. Black Wveleneh 2. If 4.00 mL of a 5.00 x 10 M stock solution is diluted to 10,00 ml, what is the final concentration? 3. The absorbance of known concentrations of red food dye were measured in order to generate the following calibration curve. a. Annotate the graph with the labels and units of the x and y axes. Also add an appropriate title. 09 b. Imagine a red food dye solution of unknown concentration was found to have an absorbance of 0.80. Using the calibration curve, estimate the concentration of the unknown dye solution. 06 05 04 200E-3 4.00E-3 8.00E- 600E-3 100E-2 193

Answer 1

part 1

750 400 nanometers 620. RED VIOLET 43 430 ORANGE BLUE 580 YELLOW GREEN 490 560

since the dye is absorbance at wavelength around 630 nm i.e it is absorbing red colour so to our eye we will see the complimentary colour that is being emitted that is green -blue colour

part 2

initial concentration =S₁= 5 *10^-5 M

initial volume V₁ =4ml

final volume V₂ =10ml

final concentration = S₂

using

V₁S₁=V₂S₂

V₁S₁ /V₂ =S₂

4 ml* 5 *10^-5 M / 10ml = S₂

20 *10^-5 M/10= S₂

2 *10^-5 M=S₂

the final concentration = 2 *10^-5 M