# How to Determine The Concentration of a Solution

The concentration of a solution describes the amount of solute
present in a given amount of a solution. The unit of concentration depends on
the units used for amount of solute and the amount of solution. According to mole concept, concentration of a solution is define as the amount of mole of solute dissolved in 1dm3 of the solution. therefore its unit is mol/dm3.
The
concentration of a solution can be expressed in three ways
Percentage composition: Concentration can be
expressed as a percentage of mass of a soluble solute compared with the
solvent. For example, a 20% sodium hydroxide is a solution that contains 20g of
sodium hydroxide (NaOH) dissolved in 100g of water since experiment has showed
that 100cm3 of water
is equivalent to 100g of water at any temperature.
Mass per dm3 concentration
in grammes of a solution
: Concentration can be expressed in grammes per
dm3,this is the mass concentration of a solution. It involves
dissolution of a known mass of solute (measured in grammes) in water and making
it up to 1000cm3 or 1dm3.
Using a graduated flask.The known mass of solute in grm is said to have been
dissolved in 1dm3 of a
solution. For example, if 10g of sodium chloride is weighed and dissolved in
1dm3 of water,
then the mass concentration or concentration of the sodium chloride solution is
10g/dm3.
Molar concentration (mol per dm3 of a solution):  Concentration can also be
expressed in mol per dm3, this is the molar concentration of a
solution. This involves the conversion of a concentration that has been known
or determined in g/dm3 to mol/dm3,
using the molar mass of a solute. For example, the molar mass of potassium
hydroxide (KOH) is 56g, if 20g of KOH is dissolved in 1dm3 of water (solvent) to form a solution, then 1dm3 of the solution contains.
Known
mass in g/dm3   ÷Molar
mass = 20gdm3÷56g = 0.36mol/dm3 or 0.35m
The
concentration of a solution of Chlorine (Cl) x Volume (V) = Mass of the solute
in g. If a solution contains 35g/dm3  and  100cm3 of that solution is used, that is 0.1dm3. Then the reacting
mass of the solute is 35×0.1 = 3.5g.
Moles of
a solution = Mass of solute/Molar mass.