Challenge question. Let’s explore why it’s important to run samples in order of increasing concentration if possible. Solutions A and B are different concentrations of the same dye measured at the same λmax. A student measures the absorbance of solution A, shakes A out of the cuvette, then adds solution B and measures its absorbance. Assume one drop of solution A was left in the cuvette when it is filled with 1.00 mL of solution B. There are 20 drops in one milliliter.

Scenario 1. You are measuring Solution B = 0.0800 M, which is 16 times more concentrated than Solution A = 0.00500 M.
a. What is the actual concentration in the cuvette?
b. What is the percent error compared to solution B’s actual concentration?

Scenario 2. You are measuring Solution B = 0.00500 M, which is more dilute by a factor of 1/16 than Solution A = 0.0800 M.
a. What is the actual concentration in the cuvette?
b. What is the percent error compared to solution B’s actual concentration?