For the students who read Chemistry all over the world

CLASS-12 CHEMISTRY



Solution
1. What is a solution?
• Homogeneous mixture of chemically non-reacting 2, or more
components.
• Components => Solute (can be 1,2,3 or more )
+Solvent(always 1)
• Binary solution => 1 solute +1 solvent= solution
2. Which component is the solvent?
• Component which is present in larger amount (by mole),
• Component which determines the phase of the solution.
e.g., - Gaseous soln (Solvent is gas)
- Liquid soln (Sovent is liqud)
- Solid soln( Solvent is solid)
3. Vapour pressure => The pressure exerted by the vapour over a liq. Surface
at eqm, is known as vapour pressure.
At equilibrium, rate of vapourization = rate of condensation

, • Units=> atm, bar, torr etc.
4. Factors affecting Vapour pressure (V.P.) =>
• Intermolecular attraction b/w the liquid molecules (inversely
proportional to V.P.)
• Temperature (T proportional to V.P.)




• Surface area
5. Roult’s law => PS = PA + PB
Where PS= Vapour pressure of solution, PA= Vapour pressure of
Solvent and PB= Vapour pressure of Solute
6. Some special cases:
• Solid solute ( Non volatile) in liquid solvent (Volatile):
PS = PA + PB (PB = 0)
PS = PA -----------(1)
Now PA is proportional to XA (XA is mole fraction of
Solvent)
So, PA =PA0XA-------(2)
From equations 1 and 2 we get
PS=PA0XA -----------(3)

Now XA+XB = 1
(XB= Mole fraction of solute)
XA= 1-XB--------(4)