post Lab

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Jan 9, 2024

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Harshita Parmar Solution Preparation and Beer’s Law Post Lab Report Questions I. Calculations (Show how you calculated the bulleted items; include units and the correct number of significant figures.) Part A: Preparing Kool-Aid Solutions Mass of mix 1 transferred: 5.0632 g - 1.0323 g = 4.0309 g Stock solution concentration: 4.0309g/1L = 4030.90 mg solids/L First dilution’s concentration: 10 mL dilution: 4030.90 x .10 = 403.090 mg solids/L II. Additional Questions 1. Which wavelength choice among those available with the Vernier colorimeter would be the best choice for a Beer’s Law experiment using strawberry Kool-Aid? Why? The wavelength of 470 nm would be the best choice for a Beer’s Law experiment with Strawberry Kool-Aid because the higher wavelengths are least absorbed, so the transmitted light is predominantly red. The greatest absorption of light is at blue (45nm) to green (510nm) to yellow (570nm) before significantly curving lower. 2. List your data and calculated concentrations for your two unknowns: Kool-Aid Flavor STD Curve slope Y-intercept Unknown ID Absorbanc e Concentratio n Cherry 0.0288 -0.017 0.282 2.463 3600 mg/L Grape 0.0098 -0.027 0.282 0.433 4000 mg/L 3. How does the wavelength of maximum absorbance relate to a substance’s color? The wavelength at maximum absorbance relates to a substance’s color because the color at the wavelength of maximum absorbance is removed by absorption and the remaining colors are reflected to the eye. The reflected color will be visible to the eye. 4. Do your stock solutions obey Beer’s Law, given your calibration range equations? Why or why not? Yes, they obey Beer’s law because the absorbance and concentration are directly proportional to each other, on the graph.
5. How did your transferred mix mass compare to the amount listed on the package label? My transferred mix mass is 4.03 g and the net weight of Kool-aid listed on the packet is 3.9 g. My transferred mix mass is slightly larger then the packet weight. 6. A lab pair’s Beer’s Law calibration graph 0.08 < A < 0.79 had a best-fit line of A = 0.013 C − 0.023. Data was: off-scale for both the stock solution and solution #1 (10.00 mL stock diluted to 25.00 mL); solution #2 (1.00 mL stock diluted to 25.00 mL) had A = 0.85, and solution #3 (1.00 mL of solution #1 diluted to 25.00 mL) had A = 0.73. What are the concentrations of solution #3 and the stock solution? A = 0.013 C − 0.023 Concentration: solution #3: 0.73=0.013 C -0.023 C= 57.93 mg/L 57.92*25*10^-3=1.440 mg = 1448 mg/L stock solution: M1V1=M2V2 M1(10)=(1448)(25) M1= 3620
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