1 Quiz 6 (Chapter 13: Dilutions) 1. How would you prepare 25 mL of a 1/15 dilution of food coloring? 2. If you take 5 mL of 250 mM NaCl and add 25 mL of water to it, what is the final concentration of NaCl in the dilution? 3. If you prepare a 1/40 dilution of a 350 mg/mL solution, what is the final concentration of the solution? 4. You do an assay (test) to determine how much protein is present in a sample. To perform the assay, it is necessary to dilute the original sample 1/100. If the assay shows that the concentration of protein in the diluted sample was 1.5 mg/mL, what was the concentration of protein in the undiluted sample? ____ 5. A flask contains 500 mL of solution. A small amount of sample was removed from the flask. This sample was diluted 1/50. The concentration of protein in the diluted sample was 2.5 mg/mL. a. What was the concentration of protein in the original sample? Express your answer in units of mg/mL. b. How much protein was present in the entire 500 mL ? 2 6. You take 100 mL of suspended bacteria and grind them into a cell paste. Then, you remove 100 L of these cells and perform a test that tells you how much protein is present. Your test shows that 30 g of protein are present in the 100 L of cell paste. What was the concentration of protein in the cell paste? a. Express your answer in units of g/L. b. Express your answer in units of mg/mL. 7. Suppose you perform the following dilution series: Step 1: You take 100 L of a bacterial culture and add 0.9 mL of media. Step 2: You take 100 L of the dilution prepared in step 1 and add 9.9 mL of media. Now, suppose you plate 0.1 mL of the dilution made in step 2 onto a plate and observe 555 colonies. A. Provide a sketch of the steps listed above (including the plating step.) B. What is the concentration of bacteria in the ORIGINAL (undiluted) culture?