SOLUTIONS & COLLIGATIVE PROPERTIES
SOLUTIONS & COLLIGATIVE PROPERTIES
INTRODUCTION For example, common salt in water.
In normal life we rarely come across pure substances. Most 1.2 Classification
of these are mixtures containing two or more pure
substances. Their utility or importance in life depends on Solutions which contain two components in it are called
their composition. The air around us is a mixture of gases Binary Solutions.
primarily oxygen and nitrogen; the water we drink contains
Substances which are used to prepare a solution are called
very small amounts of various salts dissolved in it. Our blood
is a mixture of different components. Alloys such as brass, as Components.
bronze, stainless steel, etc. are also mixtures. In this Unit, The component that is present in the largest quantity is
we will consider mostly liquid solutions and their properties. known as Solvent. Solvent determines the physical state in
which solution exists.
1. SOLUTIONS
The other component present in lesser quantity in the
solution is termed as Solute.
1.1 Definition
Each component may be solid, liquid or in gaseous state.
A solution is a homogeneous mixture of two or more than
two components.
1.3 Strength of Solutions
Mass of component in the sol.
Mass % of a component u 100
The amount of solute dissolved per unit solution or Total Mass of sol.
solvent is called Strength of solution. There are various 2. Volume percentage (%v/v):
methods of measuring strength of a solution. :
“It represents volume of a component in 100 mL of solution”
1. Mass Percentage (%w/w):
“It represents mass of a component present in 100 g of Vol. of component
Vol. % of a component = ×100
solution” Total vol. of solution
, SOLUTIONS & COLLIGATIVE PROPERTIES
3. Mass by volume percentage (%w/v): 8. Normality, N
“It represents mass of solute in grams present in 100 mL of It represents no. of equivalents of solute present in 1 L of
solution” solution.
Mass of solute in g No. of Equivalents of solute
Mass by vol. percent = u 100 Normality, N
Vol. of sol. in mL Vol. of sol. in L
4. Parts per Million (ppm)
Weight
No. of equivalents, eq
No. of parts of the component Equivalent weight (W / E)
Parts per Million u 106
Total no. of all the componens of sol.
M
E (z is the valency factor)
Concentration in parts per million can be expressed as mass z
to mass, volume to volume and mass to volume.
SOME IMPORTANT RELATIONSHIPS
5. Mole Fraction (x)
Dilution Law
“It represents the moles of a solute present in one mole of
solution” If a solution is diluted by adding solvent to it, then the
amount of solute remains constant and we can write:
No. of moles of the component
Mole fraction M1V1 = M2V2 and N1V1 = N2V2
Total no. of moles all the components
Molarity and Normality
For example, in a binary mixture, if the number of moles
of A and B are nA and nB respectively, the mole fraction Normality = z × Molarity
of A will be
IMPORTANT :
nA Mass %, ppm, mole fraction and molality are independent
xA
nA n B of temperature, whereas molarity & normality are a
function of temperature. This is because volume depends
6. Molarity, M on temperature and the mass does not.
“It represents moles of solute present in 1 L of solution”
2. VAPOUR PRESSURE
Moles of solute
Molarity, M
Vol. of sol. in L 2.1 Definition
Units of Molarity are mol/L also represented by ‘M’ or Vapour pressure of a liquid/solution is the pressure exerted
‘Molar’. by the vapours in equilibrium with the liquid/solution at a
“Density of a solution is mass of the solution per unit particular temperature.
volume” Vapour pressure v escaping tendency
Mass of sol. 2.2 Vapour pressure of liquid solutions and
Density, d m/V
Vol. of sol. Raoult’s Law :
7. Molality, m
(Raoult’s law for volatile solutes)
“It represents moles of solute present per kg of solvent”
Raoult’s law states that for a solution of volatile liquids,
Moles of solute the partial vapour pressure of each component in the
Molality, m
Mass of solvent in kg solution is directly proportional to its mole fraction.
Consider a solution containing two volatile components
Units of molality are mol/kg which is also represented by
1and 2 with mole fractions x1 and x2 respectively. Suppose
‘m’ or ‘molal’.
SOLUTIONS & COLLIGATIVE PROPERTIES
INTRODUCTION For example, common salt in water.
In normal life we rarely come across pure substances. Most 1.2 Classification
of these are mixtures containing two or more pure
substances. Their utility or importance in life depends on Solutions which contain two components in it are called
their composition. The air around us is a mixture of gases Binary Solutions.
primarily oxygen and nitrogen; the water we drink contains
Substances which are used to prepare a solution are called
very small amounts of various salts dissolved in it. Our blood
is a mixture of different components. Alloys such as brass, as Components.
bronze, stainless steel, etc. are also mixtures. In this Unit, The component that is present in the largest quantity is
we will consider mostly liquid solutions and their properties. known as Solvent. Solvent determines the physical state in
which solution exists.
1. SOLUTIONS
The other component present in lesser quantity in the
solution is termed as Solute.
1.1 Definition
Each component may be solid, liquid or in gaseous state.
A solution is a homogeneous mixture of two or more than
two components.
1.3 Strength of Solutions
Mass of component in the sol.
Mass % of a component u 100
The amount of solute dissolved per unit solution or Total Mass of sol.
solvent is called Strength of solution. There are various 2. Volume percentage (%v/v):
methods of measuring strength of a solution. :
“It represents volume of a component in 100 mL of solution”
1. Mass Percentage (%w/w):
“It represents mass of a component present in 100 g of Vol. of component
Vol. % of a component = ×100
solution” Total vol. of solution
, SOLUTIONS & COLLIGATIVE PROPERTIES
3. Mass by volume percentage (%w/v): 8. Normality, N
“It represents mass of solute in grams present in 100 mL of It represents no. of equivalents of solute present in 1 L of
solution” solution.
Mass of solute in g No. of Equivalents of solute
Mass by vol. percent = u 100 Normality, N
Vol. of sol. in mL Vol. of sol. in L
4. Parts per Million (ppm)
Weight
No. of equivalents, eq
No. of parts of the component Equivalent weight (W / E)
Parts per Million u 106
Total no. of all the componens of sol.
M
E (z is the valency factor)
Concentration in parts per million can be expressed as mass z
to mass, volume to volume and mass to volume.
SOME IMPORTANT RELATIONSHIPS
5. Mole Fraction (x)
Dilution Law
“It represents the moles of a solute present in one mole of
solution” If a solution is diluted by adding solvent to it, then the
amount of solute remains constant and we can write:
No. of moles of the component
Mole fraction M1V1 = M2V2 and N1V1 = N2V2
Total no. of moles all the components
Molarity and Normality
For example, in a binary mixture, if the number of moles
of A and B are nA and nB respectively, the mole fraction Normality = z × Molarity
of A will be
IMPORTANT :
nA Mass %, ppm, mole fraction and molality are independent
xA
nA n B of temperature, whereas molarity & normality are a
function of temperature. This is because volume depends
6. Molarity, M on temperature and the mass does not.
“It represents moles of solute present in 1 L of solution”
2. VAPOUR PRESSURE
Moles of solute
Molarity, M
Vol. of sol. in L 2.1 Definition
Units of Molarity are mol/L also represented by ‘M’ or Vapour pressure of a liquid/solution is the pressure exerted
‘Molar’. by the vapours in equilibrium with the liquid/solution at a
“Density of a solution is mass of the solution per unit particular temperature.
volume” Vapour pressure v escaping tendency
Mass of sol. 2.2 Vapour pressure of liquid solutions and
Density, d m/V
Vol. of sol. Raoult’s Law :
7. Molality, m
(Raoult’s law for volatile solutes)
“It represents moles of solute present per kg of solvent”
Raoult’s law states that for a solution of volatile liquids,
Moles of solute the partial vapour pressure of each component in the
Molality, m
Mass of solvent in kg solution is directly proportional to its mole fraction.
Consider a solution containing two volatile components
Units of molality are mol/kg which is also represented by
1and 2 with mole fractions x1 and x2 respectively. Suppose
‘m’ or ‘molal’.
