How to Calculate Dilution

 

calculations are very important in Chemistry.

First we need to understand what a dilution is: 
A dilution is when you have a solution of a certain concentration and you add more solvent (remember: the substance that does the dissolving!) to decrease the concentration. If you are adding more solvent, the volume of the whole solution is going to increase as the concentration of the solution decreases. You can solve for the concentration or volume of the concentrated or dilute solution using the equation: M1V1 = M2V2, where M1 is the concentration in molarity (moles/Liters) of the concentrated solution, V2 is the volume of the concentrated solution, M2 is the concentration in molarity of the dilute solution (after more solvent has been added), and V2 is the volume of the dilute solution.

Let’s do an example! Say you have a 12 M (M = moles/L) solution of hydrochloric acid. You want to dilute this concentrated HCl with water so that you have 50 mL of a 3 M hydrochloric acid solution. How many milliliters of the 12 M HCl will you need to prepare the 3 M solution? Well, let’s go back to our dilution equation: M1V1 = M2V2. To use this equation, we need to figure out what the problem is giving us. There is a concentrated 12 Molar HCl solution (M1) and we want to end up with 50 milliliters (V2) of a 3 Molar HCl solution (M2). So, we are solving for V1: how much of the concentrated solution we will need. Plugging the numerical values into the equation we get: (12 moles/L)(V1) = (3 moles/L)(50 mL). We can then multiply 3 moles/L by 50 mL to get 150 mL * moles/L. Then we divide 150 mL * moles/L by 12 moles/L (the units moles/L will cancel out) and we get 12.5 mL! So, we need 12.5 mL of the 12 M HCl diluted with water up to 50 mL to create a 3 Molar HCl solution.

- By TutaPoint.com tutor Kaitlyn Koenig. Kaitlyn tutors in Physics, Physical Science, Chemistry, Basic Math Skills, Algebra 2, Algebra 1, Mandarin Chinese at TutaPoint.com