Dilutions

When two solutions are mixed, the concentration CHANGES. Dilution is the process of DECREASING the concentration by adding a solvent, usually water. The amount of solute doesn't change. Because the concentration is mol/L, we can write:

C= n/V   n= CV     C1V1=C2V2

example 1
Determine the concentration when 100 mL of 0.10 M HCl is diluted to a final volume of 400 mL.

Because these are not chemical reactions, you do not have to write a balanced equation.
C1V1 = C2V2
(0.1 M) (0.100 L) = C2 (0.400 L)
C2= 0.0250 M

example 2: How much water must be evaporated from 2.00 L of 0.250 M KCl solution fo rthe final concentration to be 2.75 M?
C1V1 = C2V2
(2.00 L)(0.250 M)= V2(2.75)                        2.00 L - 0.18 L = 1.82 L
0.18 L = V2

example 3: 100 mL of 0.250 M Sodium Nitrate is mixed with 200 mL of 0.100 M Sodium Nitrate?
-Determine the # of mol of Sodium Nitrate in the resulting solution
n= CV
n1 + n2 = 0.100 L  x   0.250 mol   +   0.200 L   x  0.100 mol  = 0.250 mol + 0.200 mol

                                         1 L                                        1 L           

                                                                                                     = 0.450 mol

-Determine the final [NaNO3]  (determine the concentration)
0.0450 mol =  0.150 M

  0.300 L

Now what's the point of learning all of this if we're not going to use it?
Well we are going to use it! We're going to be doing a dillution lab! Here's a video that shows how to do some dilution!
Plus, the music is really cool :)

http://www.youtube.com/watch?v=bnQJ2q36d2E&feature=related