# Chem – molarity problem assignment

Molarity Problem Assignment (consult syllabus for due date)
Do not use Molarity Handout from web manual
To work in a laboratory it is necessary to prepare solutions and reagents used in protocols and procedures. These are examples of problems you could encounter and should be able to solve. Work the following problems (read carefully). If less than 100% are correct, the assignment will be returned to you for you to correct mistakes. The grade you receive the third time you turn your answers in, is your final grade. You must show work to receive credit, and partial credit will not be given. You may use a separate sheet for calculations.
1. The molecular weight of anhydrous calcium chloride is 110.99. How many grams do you need for 100 ml of 50 mM calcium chloride?

2. Hydrogen peroxide is supplied in a 30% solution. If your protocol calls for using a 0.1% solution, how would you make 20mL?

3. You are given a stock solution of EDTA at a concentration of 5mM, how would you dilution of EDTA with a final concentration of 5µM in a final volume of 250mL?

4. You need to prepare a stock solution of medium for your culture cells, which usually includes liquid salt solution and bovine serum. Your liquid salt solution is supplied in a 10X concentration, and you need to dilute it to 1X for use. You also need to add 100% fetal bovine serum for a final concentration of 10%. How would you make up 5 liters of this culture media using water as your solvent?

5. You have a 1mM stock solution of Arsenic to treat culture cells in a liquid medium. You need to treat your cells with Arsenic such that it has a final concentration of 5nM once it has been added to the cells. You are given 1mL of cells, and you can only add 2uL of your reagent to your cells. What concentration should you dilute the stock to so that you only have to add 2uL of Arsenic to your 1mL of cells in order to have a 5nM concentration of Arsenic?

6. The molecular weight of sodium hydroxide is 40.00. How many grams would you need for 150 ml of a 1mM solution?

7. A buffer stock solution is supplied as 50X concentration and you will need 10 liters at 1X, how would you prepare this solution?

8. To make up a solution of phosphate buffered saline (PBS), you need 5mM Na2HPO4 (anhydrous) (FW: 141.96), 0.15 M NaCl (FW: 58.44), and 1 mM KH2PO4 (FW: 136.09). How many grams of each will you need to make up 500mL of PBS?

9. You want to add PMA to 10mL of HL-60 cells so that you have a concentration of 2.5ηM. Your stock solution is 1mM. What is the volume of you stock solution you need?

10. The molecular weight of vincristine, a pharmaceutical drug, is 923.04. It is supplied in 1 mg per vial. You want to treat your culture cells with a final concentration of 5 ηM vincristine and will need 10mL of cells for your experiment. You only want to add 2µL of vincristine solution to your cells. What concentration should you make your stock solution of vincristine in order to make this 2uL addition?

(550 words)

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