Question

2. A researcher is often required to prepare solutions in the lab. Typically, a lab provides a concentrated solution. This solution must be diluted to the proper concentration. Hydrochloric acid is a common stock solution that is typically purchased at 37.0% HCl concentration (density = 1.20 g/ml). You must make 100 ml of 0.25 M HCl to do a DNA extraction experiment. How much of the 37.0% HCl concentration stock do you need to prepare this solution?

Answer 1

The easy to do this is to determine the molarity of the concentration HCl. That's
1.20 g/mL x 1000 x 0.37 x (1 mol/36.5g) = approx 12 M but you should be more accurate than that. Then use c1v1 = c2v2
12*v1 = 0.25*100

Solve for v1. That will give you the amount of concd HCl to pipet into a 100 mL volumetric flask and make to volume.

Answer 2

2.055ml