In: Chemistry
Absorbance at 540 nm of Bromocresol Purple Dilution Series
test tube | concentration of sample (ug/mL) | A540 nm | BcP dilution |
1 | 0 | 0 | n/a |
2 | 0.9375 | 0.041 | 1:16 |
3 | 1.875 | 0.08 | 1:08 |
4 | 3.75 | 0.155 | 1:04 |
5 | 7.5 | 0.306 | 1:02 |
6 | 15 | 0.614 | 0:00 |
1. The point 0/0 is an important and valid point on this graph. Why? (Explain) Explain how a hand-drawn graph and excel graph are similar or different.
2. How is the Beer’s Law equation similar to that of a straight line? Explain each component using the letter of the component and using a set of your experimental values. BCP: 0.015M
3. Evaluate your data using the Beer’s Law equation: use the absorbance reading for the highest concentration of a solution, determine the extinction coefficient for the BCP solution you were given. Do you get the same answer if you make this calculation at another concentration?
4. Select 2 random absorbance readings on your line (that you did not actually measure) and explain two different ways you can use your graph to determine the concentration of BCP (µg/mL) of the unknown solutions that might have the selected absorbance values. ***Provide the results; what values do you determine to be the concentrations of your 2 random absorbance readings?
5. Explain why we refer to a graph such as the one you just constructed as a “standard curve” or a “calibration curve.” How would a graph such as this one be useful?