Name: ______________________________________________________ Date: ______________________ Section: _______
Dilutions
Dilution is the addition of solvent, which decreases the concentration (molarity) of the solute in the
solution. The initial concentration of a solution is always greater than the final concentration. A common
example of a dilution is adding more water to a beverage that is too sweet.
Formula:
M1V1 = M2V2
M= molarity (concentration)
1= initial (start)
M1 is always greater than M2
V= volume
2= final (end)
V1 is always less than V2
Example: What is the final concentration of a NaOH solution when 100 mL of a 0.15 M solution is diluted to
150 mL? (Unknown = M2)
M1= 0.15 M
M2= unknown (?)
V1= 100 mL
V2= 150 mL (V2 > V1)
M1V1 = M2V2
0.15 M × 100 mL = M2 × 150 mL
Divide both sides by 150 mL to isolate unknown
(0.15 M × 100 mL)/150 mL= M2
M2= 0.1 M
The final concentration must always be less than the initial concentration. Since the initial was 0.15 M
and the final was 0.1 M we can conclude that the answer is accurate. Notice that the final volume was
greater than the initial volume.
Practice: How much water would need to be added to 600 mL of a 0.63 M KBr solution to give a final
concentration of 0.25 M? (Unknown = _____)
Name: ______________________________________________________ Date: ______________________ Section: _______
Assignment: Solve the following dilutions word problems. For each problem label the variables, identify
unknown, show all work, and include units.
1.) 50.0 mL of a HCl solution was diluted to 350 mL to give a final concentration of 0.80 mL, what was the
initial concentration? (Unknown = _____)
2.) 1400 mL of water was added to 100 mL of a KCl solution to give a final concentration of 0.0150 M, what
was the initial concentration? (Unknown = _____)
3.) What is the final concentration of a KOH solution when 45.0 mL of a 4.2 M solution is diluted to 250 mL?
(Unknown= _____)
4.) 200 mL of water was added to a 1.0 M solution of NaCl to give a final concentration of 0.20 M, what was
the initial volume of the NaCl solution? (Unknown= _____)