Making Dilutions

• Diluting a solution reduces the number of moles of solute per unit volume, but the total number of moles does not change.

• Higher molarity = more concentrated

Put in order from most dilute to most concentrated

• 6.0 M

• 0.05 M

• 1.05

• 1.5 M

• 5 x10-3 M

• 3.5 M

http://phet.colorado.edu/en/simulation/molarity

How can we change concentration?

• If we want to make 3.0 M hydrochloric acid, but we only have 6.0 M hydrochloric acid, what can we do?

Dilution Equation

• M1V1= M2V2

• Volumes can be in mL or L, but they must be the same on both sides.

• V is total volume of the solution, not the volume of water added!

Practice• I have 20.0 mL of 2.00 M solution. I need to make

0.400 M solution. To what volume should I add?

• M1V1= M2V2

• (2.00 M)(20.0) = (0.400 M)V2

• V2 = 100. mL

• I have 0.25 L of 3.0 M HBr. How much water should be added to produce a 2.0 M solution?

• M1V1= M2V2

• (3.0 M)(0.25 L) = (2.0 M)V2

• V2= 0.375 L

• V is total volume.

• I already have 0.25 L of HBr,

• 0.375 - 0.25 = 0.125

• So I should add 0.13 L of water