JEE Class 12 Chemistry Study Rankers Revision Notes
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JEE Class 12 Chemistry Study Rankers Chemistry Revision Notes provide a comprehensive and concise overview of key concepts, reactions, and principles crucial for excelling in the Joint Entrance Examination (JEE). Specifically tailored for Class 12 students, these notes serve as an invaluable resour...
, Study Rankers Revision Notes
CHAPTER-1
solutions
Topic-1
Types of Solutions, Expression of Concentration of
Solutions and Solubility
Revision Notes
Solution : A homogeneous mixture of two or more pure substances is known as solution.
If the constituents of the solution are two, it is called binary, if three then ternary, if four then quaternary and so
on.
Two constituents of the solution are :
(i) Solute : A substance that is dissolved in another substance in lesser amount (a solvent), forming a solution.
For example : Sugar, salt etc.
(ii) Solvent : A substance in which another substance is dissolved in larger amount forming a solution. For
example : Water, milk etc.
Study
Note: Solvent determines the physical state of the solution.
Types of Solutions : Any state of matter (solid, liquid, or gas) can act both as a solvent and as a solute during
the formation of a solution. Therefore, depending upon the physical states of solute and solvent, we can have
following nine different types of solutions :
S. No. Types of Solution Solute Solvent Examples
1. Solid – Solid Solid Solid Alloys like brass, bronze, etc.
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2. Solid – Liquid Solid Liquid Solution of sugar, salt, urea etc. in water.
3. Solid – Gas Solid Gas Sublimation of substances like iodine, camphor etc,
into air, dust or smoke particles in air.
4. Liquid – Solid Liquid Solid Hydrated salts, mercury in amalgamated zinc, etc.
5. Liquid – Liquid Liquid Liquid Alcohol in water, benzene in toluene.
6. Liquid – Gas Liquid Gas Aerosol, water vapour in air.
7. Gas – Solid Gas Solid Hydrogen absorbed in palladium.
8. Gas – Liquid Gas Liquid Aerated drinks.
9. Gas – Gas Gas Gas Mixture of gases etc.
Aqueous solution : A solution containing water as solvent is known as aqueous solution. For example, sugar
solution.
Non-aqueous solution : A solution containing solvent other than water is known as non-aqueous solution. For
example, iodine dissolved in alcohol.
Saturated solution : A solution in which no more solute can be dissolved at the same temperature is known as
saturated solution.
Unsaturated solution : A solution in which more amount of solute can be dissolved at the same temperature is
known as unsaturated solution.
Solubility : Solubility can be defined as the maximum amount of solute that can be dissolved in 100 g solvent to
form a saturated solution at a given temperature.
l Causes of Solubility :
(i) Inter ionic attraction in the solute molecules : Molecules are stabilised in the lattice due to electrostatic
forces and the energy released is known as lattice energy.
(ii) Inter molecular attraction between solvent molecules.
(iii) Solvation : It denotes the force of attraction between solute and solvent molecules.
(iv) Temperature.
,2 ] Study Rankers Revision Notes Oswaal CBSE Chapterwise & Topicwise Revision Notes, chemistry, Class – XII
l Deciding Factors for Solubility :
(i) Nature of Solute and Solvent : “Like dissolve like” i.e., polar solvents like water and ammonia can dissolve
polar solute or ionic solute while non-polar solvents can dissolve non-polar organic solutes.
(ii) Temperature : Solubility increases with increase in temperature. It increases for endothermic reaction while
it decreases for exothermic reaction.
(iii) Pressure : The solubility of solid in liquid is not affected significantly by pressure because solids and liquids
cannot be compressed.
(iv) Hydration Energy : It is the amount of energy released when ions formed by 1 mole of ions get hydrated. It
is an exothermic process.
Method of Expressing Concentration of Solution : The concentration of solution is the amount of solute present
in the given quantity of solute or solvent. It can be expressed in any of the following types :
Study
W
(i) Mass percentage : It is the amount of solute in grams dissolved per 100 gm of solution.
w
Mass of solute in the solution
Mass% of a solute = × 100
Total mass of the solution
(ii) Volume percentage V : It is defined as volume of a solute dissolved per 100 ml of solution.
v
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Volume of solute
Volume% of a solute = × 100
Total volume of the solution
(iii) Mass by volume percentage w : It is defined as mass of solute dissolved per 100 ml of solution. It is
v
commonly used in medicine and pharmacy.
Mass of solute
Mass by volume % of solute = × 100
Volume of solution
(iv) Parts per million (ppm) : It can be defined as the parts of a component per million (106) parts of the solution.
It is used to express the concentration of a solute present in trace quantities.
Number of the parts of the component (A)
ppm (A) = × 10 6
Total number of parrts of all the components of the solution
Parts per million can be expressed in three ways :
(a) Mass to mass
Mass of a component
ppm (mass to mass) = × 10 6
Total mass of solution
(b) Volume to volume
Volume of a component
ppm (volume to volume) = × 10 6
Total volume of solution
(c) Mass to volume
Mass of a component
ppm (mass to volume) = × 10 6
Volume of solution
(v) Mole Fraction : It is the ratio of number of moles of a particular component to the total number of moles of
all the components. e.g., mole fraction of component A.
nA
χA = ,
n A + nB
where nA is the number of moles of component ‘A’ and nB is the number of moles of component ‘B’.
nB
Similarly, χB =
nA + nB
Sum of mole fractions of all the components is always one.
χA + χB = 1
(vi) Molarity (M) : It is defined as the number of moles of solute per litre of solution.
Number of moles of solute W × 1000
Molarity = or M = nB or M = B
Volume of solution (in Litre) V MB × V
where nB is number of moles of solute, WB is weight of solute, V is volume of solution in ml, MB is molar mass of
solute. Unit is mol L–1 or M (molar)
(vii) Molality (m) : It is defined as the number of moles of solute per 1000 g or 1 kg of solvent.
, Study Rankers Revision Notes
Oswaal CBSE Chapterwise & Topicwise Revision Notes, chemistry, Class – XII [ 3
Number of moles of solute W × 1000
Molality = or m = n or m = B
Mass of solvent in kg W W × WA
where n is number of moles of solute, WA is weight of solvent, WB is quantity of solute, MB is molar mass of solute.
Molality and mole fraction do not change with change in temperature. Unit is mol kg–1 or molal (m).
(viii)Normality (N) : It is defined as number of gram equivalents of solute dissolved per litre of solution.
Number of gram equivalent of solute or N = WB × 1000
Normality =
Volume of solution in Liitre EB × V
where WB is mass of solute, EB is equivalent weight of solute, V is volume of solution in Litre.
Relationship between Molarity (M) and Molality (m) :
1000 M
Molality (m) =
M × M B − 1000d
where m is molality, M is molarity, d is density of the solution and MB is molar mass of solute.
Study
Relationship between mole fraction of solute (χB) and molality (m) :
χ B × 1000
m=
(1 − χ B ) × M A
where χB is mole fraction of solute, m is molality and MA is molar mass of solvent.
Henry’s Law : The relationship between pressure and solubility is guided by Henry’s Law. According to this law, ‘‘The mass
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of a gas dissolved in given volume of the liquid at a constant temperature depends upon the pressure applied.’’
It can also be stated as the partial pressure of the gas in vapour phase (p) is proportional to the mole fraction of the gas (χ) in
the solution.
p = KHχ,
where KH = Henry’s constant.
p
x
Fig. 1 : The slope of the line is the Henry’s constant, KH
l Applications of Henry’s law :
(i) To increase the solubility of CO2 in soda water and soft drinks, the bottle is sealed under high pressure.
(ii) To avoid the toxic effects of high concentration of nitrogen in blood, the tanks used by scuba divers are filled
with air diluted with, He (11.7%), N2 (56.2%) and oxygen (32.1%).
(iii) At high altitudes, low blood oxygen causes climber to become weak and make them unable to think clearly,
which are symptoms of a condition known as anoxia.
l Limitations of Henry’s law : This law is applicable only when :
(i) The pressure of gas is not too high and temperature is not too low.
(ii) The gas should not undergo any chemical change.
(iii) The gas should not undergo association or dissociation in the solution.
Know the Formulae
Number of moles of the component
Mole fraction of a component =
Total number of moles of alll the components
n1 n2
x1 = , x2 = ( x1 + x 2 = 1)
n1 + n2 n1 + n2
Number of moles of solute
Molarity (M) =
Volume in solution in Litre
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