Analysis of Food Dyes in Beverages Spectometry and Beer’s Law

In lab notebooks, fill out: Title Source Partners Date Purpose Safety considerations Materials (can glue in) Then, answer the “Pre-Lab Questions” (be sure to glue in the questions that you received in class! ) Copy down “Introductory Activity” Procedures (can glue in)

Intro Activity You would have run the stock solution and dilutions with known concentrations through the spectrophotometer to measure the %T in order to create a calibration curve so that we have something to compare an “unknown” to. The cuvettes we use are 1.0 cm.

Glue following data table in your notebooks (I put a PDF of it on my website- just print and glue.) after the Intro Activity Procedure. The %T are values that you would have acquired (or close to), if you had actually run the stock blue dye and diluted standards through the spec. Solution Dilution ratio Concentration % T T A   mL stock/mL water micromolar A (stock)  10/0  12.2 B  8/2  18.7 C  6/4  26.0 D  4/6  39.3 E  3/7  48.6 F  2/8  61.0 G  1/9  74.2 H  0/10  99.0

After copying the data table… (1) Complete #7 and 8 from “Introductory Activity” (show work!). Fill out the data table with your answers. (2) Complete #9 from “Introductory Activity”, but you only need to create 1 graph, not 5. Absorbance vs. Concentration of Dye is the only one required! Glue it in your notebook after your work for #7 and 8. BE SURE YOUR GRAPH HAS THE AXES LABELED AND A PROPER TITLE! You can use a computer program to do this, and just print and glue it in.

Calculation Hints: First convert %T to T (move decimal) Convert to Absorbance (A = -logT) Use Beer’s Law to calculate concentration (in micromolar) of each using the absorbance measured (like prelab question #3, only solving for C instead of A). Use the same value for ε that was given in prelab question #3.