solutions Flashcards
solutions
homogenous mixture of two or more components
composition of a solution can be expressed by _______
expressing its concentrations
qualitative ways of expressing a solutions concentration
dilute
concentrated
quantitative ways of expressing a solutions concentration
mole fraction, mass%, molarity, molality.
conc by ___is used in industrial chemical applications
mass%
solubility
max amount that can be dissolved in a specified amount of solvent at a specified temperature.
factors affecting solubility
- nature of solvent
- nature of solute
- temperature
- pressure
dissolution
when a solid solute is added to the solvent some solute dissolves and its conc increases in a solution.
crystallization
some solute particles collide withe the solid solute particles and get separated out of the solutions.
how eqbm is attained b/w dissolution and crystallization
- when dissolution and crystallization occur at a same rate, the no. of solute particles going out of the solution will be equal to the no of particles separating out and a state of dynamic eqbm is reached.
why pressure does not have any significant effect on solubility.
- bec. solids and liquids are highly incompressible and practically remain unaffected by changes in pressure.
Kh and solubility
inverse
temp and solubility
inverse
Kh and solubility
direct
___ was teh 1st to give teh qualitative relation b/w pressure and solubility of a gas in a solvent which is known as Henry’s law.
Henry
Henry’s law
the partial pressure of the gas in vapour phase is proportional to the mole fraction of the gas in the solution.
p=Kh X
To increase the solubility of CO2 in soft drinks
The bottle is sealed under high pressure
What is done to avoid bends in scuba divers?
- Scuba divers must cope with high concentrations of dissolved gases while breathing air at high pressure underwater. Increased pressure increases the solubility of atmospheric gases in blood. When the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and leads to the formation of bubbles of nitrogen in the blood. This blocks capillaries and creates a medical condition known as bends, which are painful and dangerous to life.
- To avoid bends, as well as, the toxic effects of high concentrations of nitrogen in the blood, the tanks used by scuba divers are filled with air diluted with helium (11.7% helium, 56.2% nitrogen and 32.1% oxygen).
Who are affected by anoxia?
At high altitudes the partial pressure of oxygen is less than that at the ground level. This leads to low concentrations of oxygen in the blood and tissues of people living at high altitudes or climbers. Low blood oxygen causes climbers to become weak and unable to think clearly, symptoms of a condition known as anoxia.
How is dissolution similar to crystallization?
Solubility of gases in liquids decreases with rise in temperature. When dissolved, the gas molecules are present in liquid phase and the process of dissolution can be considered similar to condensation and heat is evolved in this process.
Raoult’s law
Raoults law states that for any solution the partial pressure of each volatile component in the solution is directly proportional to its mole fraction.
Dalton’s law of partialpressures
The total pressure over the solution will be the sum of the partial pressure of the components of the solution.
Raoult’s law as a special case of Henry’s law.
According to Raoult’s law, the vapour pressure of a volatile component
inagivensolutionisgivenbyp =x p0.Inthesolutionofagasina iii
liquid, one of the components is so volatile that it exists as a gas and we have already seen that its solubility is given by Henry’s law which states that
p = KH x.
If we compare the equations for Raoult’s law and Henry’s law, it
can be seen that the partial pressure of the volatile component or gas
is directly proportional to its mole fraction in solution. Only the
proportionality constant K differs from p 0. Thus, Raoult’s law becomes H1
a special case of Henry’s law in which K becomes equal to p 0.
+ve déviation solution
Ethanol and acetone
Cs2 and acetone
-ve deviation
Phenol and aniline
Chloroform and acetone
Colligative property
The properties which depend on the number of solute particles irrespective of their nature relative to the total number of particles present in the solution.such properties are called colligative properties.
Rlvp =
Mole fraction of solute
Spm
Membranes in which small solvent molecules like water can pass through these holes but the passage of bigger molecules like solute is hindered.
Osmosis
The process in which solvent molecules flow from the solvent to the solution through a spm till eqbm is attained is called osmosis.
Osmotic pressure
The pressure that stops the flow of solvent is called osmotic pressure of the solution.
Edema
People taking a lot of salty food experience water retention in tissue celles and intercellular spaces because of osmosis. The resulting puffiness or swelling is called edema.
Advantage of osmotic pressure over other colligative property
- pressure measurement is around room temperature.
- molarity of the solution is used instead of molality.
- the technique of osmotic pressure for determination of molar mass of solutes is particularly useful for bio molecules as they are generally not stable at higher temperatures and polymers have poor solubility.
- the magnitude is very large for very dilute solutions.
Isotonic solution
Two solutions having the same osmotic pressure at a given temperature.
Isotonic, hypertonic and hypotonic wrt nacl solution
Isotonic= 0.9%
Hypertonic= less than 0.9%
Hypotonic= greater than 0.9%
Reverse osmosis
The direction of osmosis can be reversed if a pressure larger than the osmotic pressure is applied to the solution side. That is, now the pure solvent flows out of the solution through the semi permeable membrane. This phenomenon is called reverse osmosis and is of great practical utility.
Reverse osmosis in desalination of sea water
- diagram in tb
When pressure more than osmotic pressure is applied, pure water is squeezed out of the sea water through the membrane. A variety of polymer membranes are available for this purpose.
Use of cellulose acetate for reverse osmosis
The pressure required for the reverse osmosis is quite high. A workable porous membrane is a film of cellulose acetate placed over a suitable support. Cellulose acetate is permeable to water but impermeable to impurities and ions present in sea water. These days many countries use desalination plants to meet their potable water requirements.
when there is dissociation of solute into ions,
when there is dissociation of solute into ions, the experimentally determined molar mass is always lower than the true value.
Dimerization in ethanoic acid
Molecules of ethanoic acid (acetic acid) dimerise in benzene due to hydrogen bonding. This normally happens in solvents of low dielectric constant. In this case the number of particles is reduced due to dimerisation.
Determining association and dissociation wrt i
In case of association, value of i is less than unity while for dissociation it is greater than unity.
