CHSE SOLUTIONS NOTES AND IMPORTANT QUESTIONS
key points 👇🏻
1.Solutions: A solution is a homogeneous mixture of two or more chemically non-reacting substances, whose Compositon can be vaned within certain limits. It is
a singie phase system In a binary solution (two components only), the component which is present in larger amount is called solvent and the component which is present in smaller amount is called solute.
2. Concentration of Solutions
I) Strength (S) of a solution is the number of gram of solute present in one litre of solution.
II) Normality (N) is the number of gram-equivalent
of solute present in 1 litre of solution.
III)Molarity (M) is the numbr of moles of solue present in I litre of solution.
Units of molarity = moles per litre =mol-¹
IV)Molality (m) is the numbr of moles of solute dissolved in 1 kg of solvent.
Units of molality = mol Kg-¹
V) Mole fraction of solute is division of No of moles of solute by Total no. of moles of solute & solvent
3.Solubility of Gases in Liquids is defined as the volume of the gas (reduced to NTP) dissolved in unit volume ofsolvent (liquid) at the temperature of the experiment
and under a partial pressure of atomsphereo the gas to form a saturated solution.
4.Factors influencing solubility of a gas are:
i)Nature of gas and nature of solvent
ii) Temperature of the gas liquid system
ii) Pressure of the gas.
5.Solid Solution is a solid in which components are compatible and form a unique phase.
6.Raoult's law and Vapour pressure:
For volatile solution, vapour pressure of any
i)component in the solution is equal to the product of the vapour pressure of pure component and mole
(ii) For non-volatile solutes, relative lowering in vapour pressure is equal to the mole fraction of the solute
7.Colligative properties: Relative lowering in vapour pressure, elevation in boiling point, depression in freezing point and osmotic pressure are called colligative properties, because these depend only on the number of solute particles and not on their nature.
8.Osmosis and Osmotic pressure: Osmosis is the spontaneous flow of solvent molecules from solvent to the solution or from less concentrated solution to more concentrated solution through the semi-permeable membrane.
Osmotic pressure is the excess pressure which can be applied to a solution in order to prevent the passage of solvent molecules into the solution side through a semi-permeable membrane.
9.Van't Hoff Laws of Osmotic Pressure
Osmotic pressure of a solution at constant temperature is directly proportional to its molar concentration (c moles litl)
ii) Osmotic pressure of a solution of fixed
concentration is directly proportional to its
gas absolute temperature (T).
10. Ideal and Non-ideal solutions
Ideal solutions are formed by liquids having same are intermolecular interactions which perfectly obey
Raoult's law, e.g. benzene toluene.
11. Non-ideal solutions show deviations from Raoult's laws.
12. If intermolecular interactions increase on mixing mole the two liquids, the solution show negative deviations e.g. chloroform + acetone.
13.If intermolecular interactions decrease on mixing in the two liquids, the solution show positive deviations
e.g. ethyl alcohol+cyclohexane.
14. Electrolyte undergoing dissociation: If a solute undergoes dissociation, observed colligative property will be higher (e.g. NaCI in water) and molecular mass will be lower.
15. Solute undergoing association: Ifa solute undergoes in association, observed colligative property will be
called lower (e.g. acetic acid in water) and molecular mass only will be higher.
16. Van't Hoff factor
i=Observed colligative property/
Normal colligative property
Or
Normal molecular mass/
Observed molecular mass
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Chse Important Questions:Download now
Chse solution long questions
1)State Henry's law correlating the
pressure of a gas and its solubility in a
mention its two solvent and
applications ?
Ans. Henry's law states that the mass of a gas dissolved per unit volume of the solvent at a given temperature is proportional to the pressure of the gas in equilibrium with the solution. If m is the mass of the
gas dissolved in a unit volume and p is the pressure of the gas in equilibrium with the solution, then
m =p or m = k.p.
where k is the proportionality constant. The magnitude of k depends on the nature of the gas, nature of the solvent and temperature.
It may also be stated as the pressure of a gas
over a solution in which the gas is dissolved is type proportional to the mole fracion of the gas dissolved in
type the solution, i.e.,
x proportional to p
x = K'p
where K, is called Henry's law constant
Applications of Henry's law:
Some important applications of Henry's law are
(1) In the production of carbonated
created beverages: To increase the solubility of CO, 1n are single
drinks, soda water, beer or champagne, the bottles are sealed under high pressure. When the bottle is opened under normal atmospheric conditions, the pressure
inside the bottle falls to atmospheric pressure and the excess CO, bubbles out of the solution causing the effervescence.
2) In deep sea diving (Scuba diving). Deep
sea divers depend upon compressed air for breathing at high pressure under water. The compresed air contains N, in depths when the diver breathes in compressed air from the supply tank, more N, dissolves
in the blood and other body fluids because the pressure at that depth is far greater than the surface atmospheric pressure. When the diver comes towards the surface,
the pressure decreases.
2)Define the terms osmois and osmotic
pressure. What is the advantage of
using osmotic pressure as compared to
other colligative properties for the
determination of molar masses of
solutes in solutions?
Ans. The flow of solvent from solution of low concentration to higher concentration through a semi-permeable membrane is called osmosis.
The excess pressure which must be applied to a solution to prevent the passage of solvent through a semi-permeable membrane is called osmotic pressure.
Advantages of osmotic pressure:
Osmotic pressure measurement is preferred over all other colligative properties because,
(1) even in dilute solutions, the osmotic pressure values are appreciably high and can be measured accurately.
2) osmotic pressure can be measured at rOOm temperature. On the other hand, elevation in boling point is measured at high temperature where the solute
may decompose. The depression in freezing point is measured at low temperatures.
3)Define the following terms:
i) Ideal solution
ii) Azeotrope
(ii) Osmotic pressure
Ans. i) Ideal solution. A solution which obeys Raoult's law exactly over the entire range of concentration is called ideal solution.
ii) Azeotrope. The solutions or liquid mixtures which boil at constant temperature and can distl unchanged in composition are called azeotropes.
(iii) Osmotic pressure. The excess pressu
which must be applied to a solution to prevent the passage of solvent into it through a semi-permeable membrane is called osmotic pressure.
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