1. For each of the following dilutions, calculate the dilution factor. a. 20mL of solution in a 100mL final volume b. 500L of solution in a 2.0mL final volume c. 150L of serum is added to 300L of saline solution, and 20L of the resulting solution is added to 180L of saline solution d. 0.55mL plasma is mixed with 0.45mL of diluent e. 1.0mL of saline is mixed with 0.5mL of water 2. Propose a procedure for carrying out the following dilution: In one step, dilute 20L of serum 1:6 such that the final volume is 120L. 3. In a serial dilution of five equivalent steps, achieve a sample dilution of 1:100,000 starting with 0.20mL of solution and ending with a final volume of 2.0mL. 4. If the tube dilution is 1:3, how many tubes are required in a series to achieve a sample dilution of 1:243? 5. A technologist mixes 100L of patient sample with 300L of diluent and then multiplies the result by 3 to make up for the correct. Is this corrected concentration accurate, too high, or too low? If inaccurate, by what percentage? Additional Lab Math Practice: 1. A calcium standard solution contains 10mg/dL of calcium. What is its concentration in mm/L? 2. How much alcohol is required to prepare 5L of 70% alcohol? 3. A colorimetric method calls for the use of 0.1mL of serum, 5mL of reagents, and 4.9mL of water. What is the dilution of the serum in the final solution? 4. A stock standard solution of urea contains 10mg/mL of urea nitrogen. How much stock (in mL) is needed to prepare 200mL of a working standard containing 20mg/dL of urea nitrogen? 5. An isotonic saline solution contains 0.85% (w/v) NaCl. How many grams of NaCl are needed to prepare 5L of this solution? 6. A 1/200 stock solution of boric acid is on hand. The procedure requires 50mL of a 1/500 solution. How would the necessary amount be made without making excess? 7. When a blood sample was diluted 500 times, 300 cells were counted in the diluted sample. How many blood cells were in the original blood sample? 8. A test on a urine sample was ordered. The concentration of the substance in the urine was too high to be determined with our instruments. We made a 1/10 dilution and ran the test on the diluted solution. The answer obtained was 50 mg/mL. What should be reported as the concentration of the undiluted urine? 9. Determine the dilution factor: a. 30mg of methionine/mL diluted to 3mg/mL b. 220g of aspartic acid/mL diluted to 2.2g/mL c. 2mL of a solution diluted to a total of 8mL d. 5mL of a solution diluted to 12.5mL 10.How would you dilute a 10M antibiotic solution to a: a. 0.1M solution b. 1.0M solution c. 0.5M solution d. 0.85M solution 11. You have a 100mg/mL stock solution of methionine. You dilute 0.1mL of it in 9.9mL of water. a. What is the concentration of methionine in the diluted sample? b. If you now take 2mL of the diluted sample and add 8mL of water, what is the new methionine concentration? c. If you add 2mL of the original stock to the diluted sample in step b above, what would be the methionine concentration? 12.Diagram a serial dilution under the following parameters: Use only 3 tubes. The stock solution volume is 0.1mL. You need to achieve a 10 -6 dilution. Advanced Dilution Problems: 1. In your thesis experiment, you are determining the number of bacteriophage plaque forming units (pfu) in a particular diluted volume. Using the information provided below, determine the number of pfu/mL in the original solution. a. 75 plaques, 1/1000 dilution, 1mL plated b. 41 plaques, 1/1000000 dilution, 0.1mL plated c. 30 plaques, 1/10000 dilution, 100L plated 2. You have a stock solution with 2 x 106 bacterial/ml and you need 500mL of a solution with a concentration of 1500 bacteria/mL to run an experiment. What is one way to make this dilution? 3. Let's pretend that, on average, 1000 bacteria weigh 5ng. You have 10mL of a stock solution of bacteria. If you make a 10-6 dilution and find that you get 36 colonies when you plate 0.1mL of the dilution, what is the total weight of the bacteria in the original solution in mg? 4. If your original solution is 25mg/mL and you add 5mL of it to 495mL of saline, what is the new concentration? 5. A 0.1mL sample of lake water was spread onto the surface of an agar petri dish. After incubation, 450 colonies grew on the plate. What is the cfu count per mL of the water? 6. Back in the old days, setting up a PCR reaction consisted of adding dNTP's, buffers, enzyme, and salts to the reaction tube separately instead of the prepackaged mastermixes of today. I've made many a 2.5mM stock solution of dNTP's, which means that I have 2.5mM of each base - dATP, dCTP, dTTP, dGTP mixed together. Commercial companies typically sell the 20mM stock solution of each of these bases. How would you make 50L each of 2.5mM dNTP stock solutions