Units of Concentration
A solution is a homogeneous
mixture of one substance (the
solute) dissolved in another
substance (the solvent).
Concentration is a ratio of the
amount of solute to the amount
of solvent.
Units of Concentration
Percent volume
% volume = volume solute (ml)
volume solution (ml)
x 100
Percent mass
% mass = mass solute (g)
mass solution (g)
x 100
Solution = solvent + solute
Units of Concentration
Example 1:
What is the percent by volume concentration of a
solution in which 75.0 ml of ethanol is diluted to a
volume of 250.0 ml?
75.0 ml x 100
250.0 ml
= 30.0%
Units of Concentration
Example 2:
What volume of acetic acid is present in a bottle containing
350.0 ml of a solution which measures 5.00%
concentration?
x
350.0 ml
= 0.05
x = 17.5 ml
Units of Concentration
Example 3:
Find the percent by mass in which 41.0 g of NaCl is
dissolved in 331 grams of water.
41 g
372 g
x 100 = 11.0%
Units of Concentration
Molarity (M) is the most common unit of
concentration
Molarity is an expression of moles/Liter of
the solute.
Units of Concentration
A mole is the SI unit of number of particles and
can be used as an expression of the molecular
weight of a substance.
The formula weight of an
element is expressed as
grams/mole
Units of Concentration
The molar mass of a compound can be
calculated by adding the molar mass of the
individual elements.
22.99 + 35.45 = 58.44 g/mol
Making Solutions
You just calculated the molar mass of sodium
chloride to be 58.44 g/mol.
To determine how to make a stock solution of
sodium chloride, use the formula:
g = M x L x molar mass
Making Solutions
 How many grams of NaCl would you need to prepare
200.0 mL of a 5 M solution?
g = M x L x molar mass
g = (5mol/L) (0.2L) (58.44g/mol)
g = 58.44 g
Diluting Solutions
Often once you have made a stock
solution, you need to dilute it to a working
concentration.
To determine how to dilute the stock
solution, use the formula:
C1V1 = C2V2
C1
C2
V1
V2
– concentration of stock
- concentration of diluted solution
– volume needed of stock
– final volume of dilution
Diluting Solutions
Example 5:
How many milliliters of a 5 M stock solution of NaCl are
needed to prepare 100 ml of a 0.4 M solution?
C1 V1 = C2 V2
(5) V1 = (0.4)(100)
V1= 8 ml
Diluting Solutions
Serial Dilutions are dilutions made in series (for
example, if you needed to make solutions that
were 2M, 1M, 0.5M, and 0.25 M)
The formula for serial dilutions is:
Dilution Factor = (V1 + V2)
V1
V1 – volume of solution being diluted
V2 – volume of solvent
Units of Concentration
Example 6:
Propose a method to prepare 100 ml of a 0.5 M glucose
solution from a 5 M glucose solution.
10 = (v1 + 100)
v1
10v1 = v1 + 100
-v1
-v1
9v1 = 100
9
9
v1
=
11.1 ml of 5 M glucose + 100 ml H2O
Diluting Solutions
Dilutions tutorial