Solution Preparation Problems

Molarity practice, make the following:

1.  1 L of 2 M NaCl formula weight of NaCl = 58.45 g/mole

2.  500 mL of 1.5 M NaCl

3.  10 mL of .05 M sucrose formula weight of sucrose = 342.3g/mol

Mass/volume practice, make the following:

4.  200 mL of LB Broth 25 mg/mL LB broth powder in water

Percent practice, make the following:

Mass/volume

5.  50 mL of 1.5% agarose in buffer 1.5% is 1.5 grams into 100 mL of solution

6.  200 mL of 2% sucrose

Volume/volume

7.  500 mL of 10% bleach solution

You will start with purchased household bleach, which is a liquid and dilute the purchased bleach until it represents 10% of the total volume. 10% = 10/100.

Stock Solutions and dilutions practice, make the following:

8.  500 mL of 0.25 M sucrose using a 1 M stock solution

9.  100 mL of 0.5 mM sucrose using a 1 M sucrose solution

10.  1000 l of 2mM BSA using a 0.5 M stock solution

Challenge Problem #1:

Create 100mL of a 1 mM solution of sodium hydroxide (NaOH)

1.  Determine the mass (in g) of NaOH that you would need to create 10 mL of a 0.001M solution. (molar mass = 39.99 g/mol)

Note: this measurement of NaOH would be difficult to measure out for two reasons. NaOH comes as pellets that are quite large, and the scales that you have in your classroom are not accurate in this range.

So the next step would be to create a more concentrated stock solution and dilute it to the correct concentration for your experiment.

2.  A more reasonable measurement would be 0.3999 or about 0.400 g of NaOH, and this amount is easily dissolved into 10 mL of water. What is the molarity of the solution you would make by dissolving 4 grams of NaOH in 10 mL water?

3.  Now calculate how much of the stock solution (made in #2 above) is needed to create the 100 mL of 1 mM sodium hydroxide?


Challenge Problem #2:

Make 100 mL of 1X Tris-EDTA (TE) buffer (10 mM Tris, 1mM EDTA)

You will first make two stock solutions:

1) 100 mL of 1 M Tris-HCl (pH 7.5)

2) 50 mL of 0.5 M EDTA (pH 8.0)

1.  Below show the calculations for making a 1M stock solution of Tris-HCl

(formula weight = 121.4 g/mol).

Note: for this solution, dissolve the Tris-HCl in 70 - 80 mL of water. Adjust the pH to 7.5 with HCl. Add water to a final volume of 100 mL.

2.  Below show the calculations for making a 0.5M stock solution of EDTA

(formula weight = 292.24 g/mol).

Note: EDTA has limited solubility at pH < 8.0.

Mix the EDTA in ~40 mL of water. Stir vigorously over low heat. Slowly add NaOH to adjust the pH to 8.0 and continue mixing until dissolved. Add water to a final volume of 50 mL.

3.  Below show the calculations and include a brief description for how to make100 mL of 1X TE buffer from the two stock solutions above.

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