Dilution
Dilution: reducing the concentration of a solution by adding more solvent.
Serial dilution: taking an aliquot (small amount) of one solution, and then diluting
it with more solvent. Then taking an aliquot of that second, more dilute
solution, and diluting it further with more solvent. This process can be
continued many times. It is used to dilute a solution by quite a bit, while using
less solvent.
Standard Solution: a solution for which the precise
concentration is known. Ex: 0.2750 M solution of
HCl(aq).
Pipette: a tool used to measure out precise volumes of a
liquid. Volumetric pipettes only measure one volume
(Ex: 1.000 mL, 5.000 mL, 10.00 mL). Graduated
pipettes can measure out a variable volume (like a
graduated cylinder, but much more precise)
Volumetric Flask: A flask with a large bottom and a long thin neck. It
has a mark where the volume is precisely known.
Calculating the concentration of a diluted solutions:
Solution 1: Solution 2:
n1 n2
C1 n1 C1 V1 C2 n2 C2 V2
V1 V2
But, n1 = n2
Therefore, C1 V C2 V2
1
Examples:
1. You would like to prepare 100 mL of a 0.150 M solution of HCl(aq) from a
stock solution that is 12.0 M. What volume of the stock solution would you
need to add to the volumetric flask to prepare this solution?
2. You pipette 5.000 mL of a 2.50 M solution of NaOH(aq) into a 50.00 mL
volumetric flask. You fill the volumetric flask up with water until the mark.
What is the final concentration of this solution?
3. You take a 1.000 mL aliquot of a solution with an unknown concentration
and place it in a 100.00 mL volumetric flask. You fill the flask with water up
to the mark. You then titrate the solution and find that it has a concentration
of 0.0357 M. What is the concentration of the original solution?