Question

1. How to make 20ml of 3M NaCl?

2. What is the percent concentration of 3M NaCl?

3. What is the molar concentration of 10% NaCl?  

4. Your stock solution is 5M NaCl and your goal is to make 25ml of 0.5M NaCl (all in water). What volume of stock should you use?

5. Make a reagent solution for enzymatic digestion of plasmid in water.

The reaction conditions require:

2x digestion buffer                                               

0.5% bovine serum albumin

10 mM sodium chloride

You have 20 samples requiring 50ul of this mixture.

You have:

10X stock solution of digestion buffer

A 10% stock solution of albumin

A 1M stock solution of NaCl

Define the volume of water required to obtain the final solution volume.

6. How to make 200ml of Yeast Growth Medium in water?

Yeast Growth Medium:

56 mM glucose

20 mM HEPES

You have dry (powder):

HEPES     MW 238.3

Glucose    MW 180.16

Answer 1

1) MW of NaCl = = 58.44 g/mole.

V = 20ml = 0.02 L.

C = 3M

(V x C x MW) = 0.02 L X 3 M X 58.44 g/mole = 3.506 g NaCl dissolved in 20 ml water.

2) The percent concentration = 3.506 x 100 /(20+3.506) = 14.92%.

3) 10% NaCl solution has 10g of NaCl in 100ml of solution or 100g of NaCl in 1000ml.

Molarity = 100/58.44 = 1.711 moles of NaCl.

Therefore the molar concentration of a 10% NaCl solution is 1.711 M NaCl.

4. C1 = 5M, V1 = ? C2 = 0.5M, V2 = 25ml

We have C1 x V1 = C2 x V2 => V1 = C2 x V2 / C1 = 0.5 x 25 / 5 = 2.5 ml

Volume of stock solution required is 2.5 ml.