Beers Law (Pre Lab Assignment)

This experiment covers the concept of molarity, dilution, and Beerâs Law. Show your work and use significant figures.

a) Step 1 in the procedure of this experiment requires you to make 500.00 mL of 1.90Ã 10^-4 M Allura Red (MW 496.42 g/mol). How many grams of Allura Red would you need to weight out? Show your calculation below.

b) Suppose the molarity of Allura Red in your stock solution is 1.90Ã10^-4M and you take 5.00 mL of this solution, place it into a 100.00 mL volumetric flask and fill it to the mark with distilled water. What is the concentration of the diluted solution (dilution)? Show your work below.

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A) Calculate the mass of Allura Red (use MW=496.42 g/mol) required to produce 500 mL of a 1.90x10^-4 M solution.=0.0472gCalculations:Standard stock solutions 1 mL, 5mL, 10mL, and 15mL.Measured Allura Red: 0.0459gCalculate the molarity of each stock solution, please show work.B) Calculate the concentration of Allura Red present in the soft drink when made up according to the package instructions.Add 1 cup sugar or 1 cup splenda. Add cold water & ice to make 2 quarts; stir to dissolve. Cherry Kool-Aid package.1) A student finishes with her std soln 1 and properly, thoroughly rinses out the 100mL volumetric flask using distilled water. Then, however, she immediately proceeds to pipet 5 mL of stock solution into the volumetric flask w/o making any attempt to dry or shake out the residual water in the flask. What effect will this have on her std sol. 5? Will the concentration be too large? Too small? Explain.2) Many common materials that we ingest, though quite safe in reasonable quantities, become toxic when taken in very large doses. A measure of toxicity is the LD50 (Lethal dose, 50%). It is the quantity of material, expressed in mg of material per kg of subject-body-weight that, if administered to a population of subjects, will cause 50% of the population to perish. The LD50 value for FD&C Red Dye No. 40 is > 10,000 mg/kg in rats.Assume LD50 value for humans is the same as for rats. Calculate the number of mg of Allura Red present in an eight-ounce glass of beverage you used in this lab. How many such glasses would a typical adult human have to ingest in order to reach the LD50 concentration (10,000 mg/kg)? Be sure to state explicitly any major assumptions you make in order to do the calculation. Considering only the potential acute toxicity of Allura Red and neglecting anything else that may be present in the drink mix, do you believe the beverage mix you analyzed is a safe product?3) Calculate the volume of aqueous waste that you produced while completing this experiment. Use this value to calculate the volume of aqueous wast that would be produced by a General Chemistry course with 500 students enrolled.This lab procedure has been frequently performed using copper sulfate pentahydrate (CuSO4*5H2O) instead of Allura Red. Consult the MSDS for copper sulfate pentahydrate to determine concerns associated with this compound and appropriate methods of disposal. Would you be able to pour this waste down the drain as you did the Allura Red waste?

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3a. If the molar absorptivity constant for the red dye solution is 5.56Ã104 M-1 cm-1 , calculate the molarity of the red dye solution with absorption = 0.900. You may assume L = 1.22cm. Hint: A=ÎµLC

b. Convert the molarity in part a to w/v%. Show your work. Molar mass of FD&C red #3 = 879.86g/mol w/v% is defined as weight (in grams) of solute/100 mL of solution You should remember that w/v% always refers to the grams of materials in 100mL of solution. ppm is defined as mg of solute/ L of solution (1mg = 10-3 g) ppb is defined as Âµg of solute / L of solution (1Âµg = 10-6 g)

c. If you want to dilute the red dye solution in part a by 5 times in a single dilution step, explain in two sentences on how one should proceed with the dilution. In addition, what is the final concentration of the diluted solution? Show your work for the numerical part of this question. You are only allowed to use a 5-mL volumetric pipet, a 10-mL volumetric pipet, a 50-mL volumetric flask and/or a 100-mL volumetric flask during the dilution. You may NOT reuse the same pipet during the dilution.

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