Dilution problems

Useful equations and facts

1. CsVs = CfVf where C = concentration, V = volume, s = stock, f = final

2. CV = mass

3. Fold dilution = Vf/Vi where f = final and i = initial

4. A 1% solution is 1 g of solid dissolved in 100 mL of liquid

5. Concentrations can be shown in various ways. For example, molarity, %, X (10X stock, 5X stock etc),

molality, units/unit volume etc.

6. 1 M = 1000 mM. 1 mM = 1000 μM

Dilution problems 8 points

Review the example problems in your lab exercise. Solve the additional problems below. Problem 2 will

walk you through the formulas you need to find the solution.

1. Dilutions often require you to express display very large or very small numbers in scientific notation.

Convert the following numbers into scientific notation (exponents).

a) 980000000

b) 0.00001

c) 0.00045

d) 50000

2. a) To make 300 mL (final volume) of a 2% NaCl solution (final concentration) using a 10%

stock solution (stock concentration), how much stock solution would you add (stock

volume)? Note that there is only 1 variable. Use equation 1 above to find the solution.

b) How much water is needed? (Subtract the volume of stock solution from the final volume)

c) What is the fold-dilution? (Use equation 3 above. Note that the initial volume is the

volume of the stock solution you are adding).

3. a) Make 300 mL of 1.7% NaCl using a 20% stock solution of NaCl. How much stock

solution is needed?

b) How much water is needed?

c) What is the fold dilution?

4. Using the stock solutions shown below, make 300 mL of buffer containing 10 mM Tris, 1

mM acetate, and 1 mM EDTA.

Stocks: 0.5 M Tris, 100 mM acetate, 10 mM EDTA

List the volumes of each stock you would add to prepare your solution and how much

water you would need. Note that you will need to calculate the volume of each stock to be

added separately.

5. Convert 500 mM to M. 500 mM = _____M

6. a) You add 10 mL of 2% acetic acid to 90 mL of water.

What is the final concentration?

b) You then use this new stock you just prepared and add 10 mL of your new stock to 90 mL

of water.

What is the final concentration?

c) You repeat this process added 10 mL of your newest stock to 90 mL of water. What is the

final concentration now?

d) What is this dilution progression called?

7. What is the total mass of bovine serum albumin (BSA) when a 4% solution of BSA is made

in 50 mL of water? Recall that 1% = 1g/100mL

8. Make 500 mL of BSA at a concentration of 0.05 mg/mL. How much powered BSA do you

weigh out (equation 2 is useful here)?