Solutions Flashcards
V.P of pure water =
1.013 bar
Rate constant depends on
Temp
Henry’s law
Pressure of gas above the sol is directly proportional to mole fraction of gas inside the sol.
Pressure depends on
Nature of solute, temp, nature of solvent
Application of Henry’s law
- Preparation of soda water
- Oxygen cylinders by scuba divers which are compressed & diluted with He
- Used in high altitude to prevent anoxia
Vapour pressure of a liquid
Pressure exerted by vapours of liquid at eq.
Factors affecting vapour pressure
- Nature of liquid: If intermolecular forces are strong, V.P is less
- Temp: directly prop
Raoult’s law
In liquid-liquid sol, partial pressure exerted by one component is directly prop to its mole fraction in sol
Effect of adding non-volatile solute to volatile solvent
VP decreases. So pressure exerted above the sol. is prop only to mole fraction of solvent
Ideal sols
That obey Raoult’s law
Ideal sols examples
n-hexane & n-heptane, benzene & toluene, chloroethane & bromoethane
For +ve deviation, P >
P`X
For +ve deviation, process is
endothermic
In endothermic process, ΔH(mix) & ΔV(mix) is
+ve
For ideal solns, ΔH & ΔV is
0
+ve deviation examples
ethyl alcohols & acetone, carbondisulphide & acetone, ethyl alcohol & water
-ve deviation examples
Nitric acid & water, CCl4 & acetone, Phenol & aniline
When intermolecular H bond is less, solns show ____ deviations
+ve
Azeotropic mixture
Mixture in which components have a definite BP & has the same composition in liquid & VP
Min boiling azeotropic mixture
Mixture in which BP of mixture is less than BP of individual components
Min boiling azeotropic mixtures show _______ deviation
+ve
Examples of Min boiling azeotropic mixture
Ethanol & water
Examples of max boiling azeotropic mixture
HNO3 & water
Colligative properties
Those properties which depends on amount of solute & not its nature
K(b) is called
molal elevation/Ebullioscopic const
K(f) is called
molal depression/Cryoscopic const
Applications of depression in freezing point
- In cold countries, to avoid freezing of water in radiators of cars, ethylene glycol is added
- To remove snow blocks on roads, it is sprinkled with NaCl
Osmotic pressure
Min excess pressure to be applied on sol. to stop osmosis
Desalination of sea water
Applied pressure is more than osmotic pressure to extract salt from sea water
Osmosis
Movement of solvent from higher to lower conc. via semi-permeable membrane
Osmotic pressure is applicable only to
dilute solutions
Use of osmotic pressure
- Calculate MM of macro molecules like proteins & polymers
Advantage of osmotic pressure
It is done at room temp & molarity is used instead of molality
Polymers have ______ solubility
less
Isotonic solns.
Solns. with same osmotic pressure
hypertonic solns.
Soln. having more osmotic pressure than another
Osmosis doesn’t take place for
isotonic solns.
When is MM abnormal?
When solute of electrolyte undergoes associaton or dissociation which increases or decreases no. of particles
Van’t Hoff factor increases when
Conc decreases or no. of ions increases
Why is decrease in temp of ethanol & acetone observed?
They form a non-ideal sol with +ve deviation which increases vol
When does a sol freeze?
When its vapour pressure equals the vapour pressure of pure solid solvent.
-ve deviation ___________ temp
increases
λ(m) increases rapidly for
weak electrolytes
Lowering of V.P _____________ B.P
increases
Define fuel cell
A fuel cell is an electrochemical cell that generates electrical energy from fuel via an electrochemical reaction
Why is it not possible to obtain pure ethanol by fractional distillation?
Due to const composition so it forms an azeotrope
What general name is given to binary mixtures which show deviation from Raoult’s law
Azeotropes
If BP is higher than that of the 2 liquids, it shows
large -ve deviation from Raoult’s law
If rn is endothermic, when temp increases solubility
Increases
Factors affecting solubility
Stronger intermolecular forces, more soluble in water
Temp increases, it decrease if rn is exothermic
Pressure more solubility more
