18. If I need to dilute a 12 M hydrochloric acid solution and make 300 mL of a 0.100 solution, how much of the 12 M hydrochloric acid do I need?

Explanation:

A 300-ml of 0.100M HCl solution contains

0.100M HCl = (0.100 mol HCl/L) × (0.300 L)

> 0.03 mol HCl

So we need to find the volume of 12M HCl solution that contains 0.03 mol HCl

0.03 mol HCL = (12 mol HCl/1 L)×V

or

V = (1 L × 0.03 mol HCl)/(12 mol HCl)

= 0.0025 L

= 2.5 ml

So you need 2.5 ml of 12M HCl to be diluted with distilled water to 300 ml in order to get a 0.100M HCl solution.