Last Minute Revision

MINIMUM LEVEL OF
LEARNING (MLL)
2025-26
SUBJECT: CHEMISTRY
CLASS: XII

, CHAPTER-1 SOLUTION GIST POINTS
Concentration of Solutions:-
w/w% Composition: Mass of solute present per 100 g. of solution




Molarity [M]: No. of moles of solute present per liter of solution in called ‘molarity of solution’.
. It is temperature dependent. M= No. of Moles of solute / Volume of solution in
litre

Molality [m]: No. of moles of solute present per kg. of solvent is called molality. It is
temperature independent. m= No. of Moles of solute / Mass of Solvent in Kg

Normality[N]: No. of gram equivalent of solute present per liter of solution is called normality of
solution.

N = No. of gm equivalent of solute / Volume of solution in litre

Parts Per Million [ppm]: It is used for very dilute solutions, Parts of solute in per million parts of
solution are called ppm. Ppm = Part of solute x106 / Part of solution

Mole Fraction: Ratio of moles of components to total no. of moles of all the components
of solution is called mole fraction (x) of the component.

Henry’s law :- “The partial pressure of the gas in vapour phase p is proportional to the mole fraction of the
gas x in the solution.” P=KH x
Applications of Henery Law(1) In Packing of soda/ Soft drinks(2) In Deep see diving( He = 11.7 % , N2 = 56.2 %
and O2 =32.1% ) (3) Functions of lungs (4)At high altitudes pressure is low there for breathing problems lead to
ANOXIA (unable to think and weak)
Vapour Pressure: The pressure exerted by vapours over the liquid surface at equilibrium is called vapour
pressure of the liquid.
Raoult’s Law:“The V.P. of any volatile component in the solution is directly proportional to its mole fraction”.
Raoult’s Law for Solutions Containing Non-Volatile Solute Raoult’s Law for Solution Containing Volatile Solute




Ideal and Non-Ideal Solutions:
Ideal Solution Non Ideal Solution

Follows Raoult’s law at all temperature and Does not follow Raoult’s law at all
concentrations. P = PA + PB temperature and pressure. P ≠ PA + PB
Intermolecular forces in resulting solution are same as Intermolecular forces in resulting solution
in pure components. are different from the inter molecular force
A–B=A–A=B–B of pure components.A – B ≠ A – A, B – B
No change in volume while mixing components. Change in volume while mixing components.
Δ V mix = 0 Δ V mix ≠ 0

, No heat change take place while mixing the Heat changes take place while mixing the
components. Δ H mix = 0 components. Δ H mix ≠ 0
Eg: n – hexane + n – heptanes & benzene + toluene Eg: Acetone + Water &Acetone + CHCl3
Non Ideal Solution
Showing Positive elevation from Raoult’s Law Showing Negative Deviation from Raoult’s Law
Vapour pressure of resulting solution is greater Vapour pressure of resulting solution is less than
than sum of partial pressure of components. P> sum of the partial pressure of pure components.
PA + PB P < PA + PB
Resulting intermolecular force is weaker than pure Resulting intermolecular force is stronger than
components. pure components.
Δ V mix = +ve Δ V mix = –ve
Volume of solution > Sum of volume of Volume of solution < Sum of volume of
pure components pure components
Δ H mix = +ve Endothermic mixing process Δ H mix = –ve Exothermic process
Acetone + Water Acetone + CHCl3, HNO3 + H2O
Alcohol + Water
Carboxylic Acid + Water




Azeothrpes: (Constant Boiling Mixture) :-Solution in which components are present in a fixed proportion,
boils at a constant temperature irrespective of boiling point of pure components
๏ Minimum Boiling Azeothrpes: Boils at a temperature lower than b.ps. of pure components. [95% Alcohol]
๏ Maximum Boiling Azeothrpes: Boils at a temperature higher than b.p.s. of pure components. [68% HNO3]
Colligative Properties:- The properties of dilute solutions which depend only on number particles of solute
present in the solution and not on their identity are called colligative properties
1-Relative Lowering of Vapour Pressure The relative lowering of vapour pressure of a solution
containing a non-volatile solute is equal to the mole fraction
of the solute present in the solution.


2-Osmosis and Osmotic Pressure Osmosis:- The phenomenon of the passage of pure solven
Diffusion:-Movement of solute particles from a region of lower concentration (of the solution) to a region
from higher cone to lower cone.
of its higher concentration through a semi-permeable
E.g. Incense stick membrane.
Osmotic Pressure: Excess pressure which Reverse Osmosis: If pressure greater than osmotic pressure is
must be applied to a solution in order to
applied then, flow of solvent molecules is reversed, i.e. from a
prevent flow of solvent into the solution higher concentration solution to lower concentrated solution.
through the semi-permeable membrane.
This phenomenon is called “Reverse Osmosis”. It is used in
V = nRT = Osmotic pressure R
water purification and desalination of water.
=Gas constant
3- Elevation of Boiling Point : ΔTb m [molality]
Difference between boiling of
solution containing non volatile ΔTb = Kb m
solute and B.P. of pure solvent is Kb=Molal ElevationConstant
called elevation of B.P.

ΔTb = Tb – Tob

, 4-Depression of Freezing Point ΔTf m [molality]

Difference in freezing point of pure ΔTf = Kf m
solvent and freezing point of
solution is called ‘Depression in Kf =Molal Depression Constant
Freezing Point’.
ΔTf = T0 – Tf
f




Van't Hoff Factor:




Association Dimerisa Trimerisatio Tetrameris pentamerisati
tion n ation on

i= 1/2 1/3 1/4 1/5

dissociation NaCl MgCl2 AlCl3 K4 [Fe(CN)6]

i= 2 3 4 5




CHAPTER-2 ELECTROCHEMISTRY
SNO. Terminology
1. 1
Conductance : Reciprocal of the resistance G  Unit is 1
R
2 Specific Resistance/Resistivity :
ρ= R A /l
Unit is ohm-cm
3 Specific Conductance or Conductivity :
k= 1/ρ = l/ RA
Conductivity of any conductor is the reciprocal of specific resistance and is denoted by  (Greek work Kappa) unit Scm-1
4 Molar Conductivity : It is defined as the conducting power of all the ions produced by one gram mol of an electrolyte in a
solution. It is denoted by m unit Scm2mol-1.
 1000
m 
Molarity