Solution Concentration
In general, the concentration, c, of any solution is
expressed by the ratio:
𝑞𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒
𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 =
𝑞𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛
A concentrated solution has a higher solute to
solution ratio compared to a more dilute solution.
But these are only relative terms.
Percentage Concentration
3 ways to express percentage concentration:
-Percentage volume by volume (% V/V)
-Percentage weight by volume (%W/V)
-Percentage weight by weight (%W/W)
#1
“percentage volume by volume”
“% V/V”
Vsolute
c
 100%
Vsolution
-Usually used to express concentrations of liquids
dissolved in liquids.
#2
“percentage weight by volume”
“% W/V”
msolute
c
 100%
Vsolution
-mass must be in grams
-volume must be in mL
Example:
A 250 mL bottle of isopropyl alcohol is advertised as
being 70% W/V. What is the mass of alcohol in the
bottle?
#3
“percentage weight by weight”
“% W/W”
msolute
c
 100%
msolution
-Can use any unit of mass, but must be the same on
the top and bottom.
Parts per million concentration (ppm)
For very dilute solutions, we use a special ratio
called parts per million (ppm).
A concentration of 1 ppm means there is a million
times more solution than solute (imagine 1 drop in
a bathtub full of water).
1 ppm = 1 mg/kg = 1 mg/L = 1 g/106 mL
Amount concentration
-Since chemical reactions are represented by moles,
it is useful to represent concentration in moles as
well. This is the “amount concentration”.
n
c
V
-Units: mol/L or M
-can be indicated by putting square brackets
around a chemical.
e.g. [NaOH(aq)]=1.5 mol/L
“the amount concentration of sodium
hydroxide in water is 1.5 moles per litre”
Percentage Volume by Volume (% V/V)
Vsolute
c
 100%
Vsolution
Percentage Weight by Volume (% W/V)
msolute
c
 100%
Vsolution
Percentage Weight by Weight (% W/W)
msolute
c
 100%
msolution
Parts Per Million
1 ppm= 1mg/kg = 1 mg/L
Amount Concentration
n=amount of solute in moles
V=Volume of solution in Litres
n
c
V
Review
Molecular compounds
-Solubility can be predicted by polarity (like
dissolves like)
-Do not form ions in a solution*
-Do not conduct electricity* (non-electrolyte)
-Do not affect litmus*
-C6H12O6(s)  C6H12O6(aq)
*unless they are an acid
Ionic Compounds
-Solubility can be predicted using solubility
chart
-Dissociate to form ions in a solution
-Conduct electricity in solution (electrolyte)
-Do not affect litmus paper*
*unless they are a base
-LiBr(s)  Li+(aq) + Br-(aq)
Acids
-Molecular compounds
-Ionize to form ions in a solution
-Cation is H+(aq)
-Conduct electricity (electrolyte)
-Turn litmus paper red
-HNO3(s)  H+(aq) + NO3-(aq)
Bases
-Ionic compounds
-Dissociate to form ions in a solution
-Anion is OH-(aq)
-Conduct electricity (electrolyte)
-Turn litmus paper blue
-KOH(s)  K+(aq) + OH-(aq)
Energy Changes
-Breaking bonds absorbs energy (endothermic)
-Forming bonds releases energy (exothermic)
-Both occur during dissolving, but the net
energy change determines if it is exothermic or
endothermic