1. Dilutions Solution A Solution B Solution C
500 g of solute in 100 mL of solvent
Solution B
100 g of solute in 100 mL of solvent
Solution C
1 g of solute in 100 mL of solvent
Dilutions

2. C11-4-16 CONCENTRATION AND DILUTION
OUTCOME QUESTION(S):
C CONCENTRATION AND DILUTION
Differentiate among the various representations of concentration, and solve concentration problems.
Solve problems involving the dilutions and combinations of common solutions.
Include: stock solutions
Vocabulary & Concepts 

3. Labs buy highly concentrated solutions to save storage space – stock solutions.
Dilution: adding more solvent to small volume of stock without adding more solute.
moles from the stock = moles in the dilution
nstock = ndilution
Dilution is just “watering it down” – the moles don’t change

4. Stock
Prepared Dilution
nstock = ndilution
The moles taken in the sample of stock are all the moles present in the diluted solution

5. Remember how to find moles…
nstock = ndilution n M = V
Remember how to find moles…
creates
C1V1 = C2V2
M1V1 = M2V2
Where: C1 is the initial (stock) concentration (molarity)
V1 is the initial (stock) volume taken
C2 is the concentration (molarity) of the dilution
V2 is the final volume of the dilution

6. Try to make a rough estimate of the
If mL of water is added to mL of a mol/L solution of NaCl, what is the new concentration? C1 V1 = C2 V2
Try to make a rough estimate of the
answer…
V2 =
= mL
1 L
= L
1000 mL
(0.100)
(0.300) = M
(0.800)

7. It’s a good habit to always convert to litres
What is the concentration of the stock solution if 50.0 mL of the stock is diluted to make mL of a M solution? C1 V1 = C2 V2
(0.400 M)
(0.220 L)
1.76 mol/L C1 =
( L)
It’s a good habit to always convert to litres

8. How much water must be added to 25. 0 mL of a 1
How much water must be added to 25.0 mL of a 1.00 M stock solution of NaOH to make a M solution? C1 V1 = C2 V2
Look at the two concentrations… estimate the
answer
(1.00)
(0.0250) =
0.250 L
(0.100)
0.250 L – L = L
225 mL of water must be added to make a final volume of 250 mL

9. Making A Dilution: 1. Calculate the volume of stock needed.
2. Transfer measured stock to a second volumetric flask.
3. Add more solvent to dilute to the correct final volume.
4. Mix.

10. Don’t try to memorize this…
Mixing Solutions:
Same solute but different concentrations
Sometimes called “marrying” solutions
Total moles
CFinal =
Total volume
mol1
mol2 =
(C1V1 + C2V2 + …)
CFinal
(V1 + V2 + …)
total volume
Don’t try to memorize this…
understand it

11. 450. 0 mL of a 0. 150 M NaCl solution is mixed with 125 mL of a 0
450.0 mL of a M NaCl solution is mixed with 125 mL of a M NaCl solution.
Total moles
CFinal =
Total volume
mol1
mol2 =
(0.150)(0.450) + (0.220)(0.125) CF
( )
total volume CF =
0.165 M

12. C11-4-16 CONCENTRATION AND DILUTION
CAN YOU / HAVE YOU?
C CONCENTRATION AND DILUTION
Differentiate among the various representations of concentration, and solve concentration problems.
Solve problems involving the dilutions and combinations of common solutions.
Include: stock solutions
Vocabulary & Concepts