Solutions and Units
of Concentration
FUNDAMENTALS
May 11, 2015
What is a Mixture?
Types of Mixtures
Definitions

A solution is a homogeneous mixture

A solute is dissolved in a solvent.
– solute is the substance being dissolved
– solvent is the liquid in which the solute
is dissolved
Definitions Continued

Dilute: a solution with a small amount of solute

Concentrated: a solution with a large amount
of solute

A saturated solution is one where the
concentration is at a maximum - no more
solute is able to dissolve

A super-saturated solution is one where the
concentration has more solute than it can
normally dissolve

Solubility: a measure of how easily a solute
dissolves in a solvent
Some Examples
Solute
Solvent
Example
solid
solid
Alloys (brass, steel)
solid
liquid
Salt water
gas
solid
Air bubbles in ice cubes
liquid
liquid
Ethanol in water
gas
liquid
Soft drinks
gas
gas
Air
Solubility
We can measure how easily a
solute will dissolve in a certain
solvent.
 This measure is called solubility

Dissolution of Solid Solute
What are the driving forces which cause
solutes to dissolve to form solutions?
1. Covalent solutes dissolve by H-bonding
to water
2. Ionic solutes dissolve by dissociation
into their ions.
Concentrations: MOLARITY (M)
moles of solute
M=
L of solution



n
(moles)
M
V
(liters)
Concentration of moles of solute per
given amount of volume
Concentration measurement
Because volume is temperature
dependent, molarity can change with
temperature
Concentration: Molarity Example #1
Calculate the molarity of the
following solution:
1) 2.3 moles of sodium
chloride in 0.45 liters of
solution
M = moles of solute = 2.3
liters of solution
0.45
M = [ 5.11 M ]
n
(moles)
M
V
(liters)
Concentration: Molarity Example #2
Calculate the molarity of the following
solution:
2) 10.3 moles of LiOH in 250 mL in
solution.
**Need to convert mL to L (÷ by 1000)
M = moles of solute = 10.3 moles = 41.2M
liters of solution
0.250 liters
Concentration: Molarity Example #3
Calculate the moles of
the following solution:
3) How many moles
are needed to make
2 L of a [5.5 M]
solution of NaOH?
M = n (moles)
V (liters)
[5.5M] = n (moles)
2 Liters
n = 5.5 x 2 = 11 moles
n
(moles)
M
V
(liters)
Concentration: Molarity Example #3
Calculate the moles of the
following solution:
3) How many grams is
this?
Need MOLAR MASS of
NaOH: 40 grams
n = 11 moles
11 moles x 40 g = 440 g
n
(moles)
M
V
(liters)
Na: 23 g
O: 16 g
H: 1 g
TOTAL:
40g