Chemistry 2 Marks Questions

As ∆G = ∆H –T∆S
The process is spontaneous when ∆G is –ve. Since T = 0 so T∆S = 0, i.e ∆G = ∆H. For an exhothermic process, ∆H is –ve, therefore at absolute zero ∆G will always be –ve and hence a spontaneous process.
At temp. above absolute zero, ∆S is not zero. It may be +ve or –ve. Hence we have to consider both the ∆H and T∆S for deciding ∆G and the spontaneity.

1. As solubility of gases decreases with increase of temperature, less oxygen is available in summer in the lakes/as cold water contains more oxygen dissolved.
2. They will shrink, due to osmosis.

1. Raoult's law states that for a solution of volatile liquids, the partial vapour pressure of each component in the solution is directly proportional to its mole fraction.
2. Henry's law states that at a constant temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas over the solution.

The flow of solvent from solution of low concentration to higher concentration through semipermeable membrane is called osmosis. The hydrostatic pressure that has to be applied on the solution to prevent the entry of the solvent into the solution through the semipermeable membrane is called the Osmotic Pressure.
Advantage: Unlike other colligative properties, osmotic pressure is used to determine the Molar mass of macromolecules/polymers like protein.

Raoult’s law states that for a solution of volatile liquids, the partial vapour pressure of each component in the solution is directly proprtional to its mole fraction.
When the solute-solvent interaction is weaker than those between the solute-solute and solvent-solvent molecules then solution shows positive deviation from Raoults law hence the partial pressure of each component is greater. ex. mixture of ethanol and acetone or carbondisulphide and acetone behave in this manner.

The relative lowering of vapour pressure of a solution is equal to the mole fraction of the solute. / The vapour pressure of a solution of a non- volatile solute is equal to the vapour pressure of the pure solvent at that temperature multiplied by its mole fraction.
Negative deviation due to formation of Hydrogen bond between chloroform and acetone.

1. If the molar mass calculated by using any of the colligative properties to be different than theoretically expected molar mass
2. Extent of dissociation or association or ratio of the observed colligative property to calculated colligative property

For the solution containing volatile components, the partial vapour pressure of each component is directly proportional to its mole fraction. In both cases, p ∝ x/ Henry’s Law is a special case of Raoults Law.

1. Properties that are independent of nature of solute and depend on number of moles of solute only.
2. Number of moles of solute dissolved per kg of the solvent.

1. Azeotropes are binary mixtures having the same composition in the liquid and vapour phase and boil at a constant temperature.
2. Minimum boiling azeotrope.

eg - ethanol+water.

When the vapour pressure of a non-ideal solution is either higher or lower than that predicted by Raoult’s law, the solution exhibits deviations. These deviations are caused because of unequal intermolecular attractive forces between solute-solvent molecules and solute-solute or solvent-solvent molecules. Positive deviation eg: Mixture of ethanol and acetone, Carbon-disulphide and acetone. Negative deviation eg: Chloroform and acetone, nitric acid and water.

Molality (m) is the number of moles of the solute per kilogram (kg) of the solvent whereas Molarity is the number of moles of solute present in one litre (or one cubic decimeter) of solution.
Molality is independent of temperature whereas Molarity is function of temperature because volume depends on temperature and the mass does not or Molarity decreases with increase in temprature.

Material used for making semipermeable membrane for carrying out reverse osmosis is- "a film of cellulose acetate placed over a suitable support."

A membrane that permits the flow of solvent molecules not the solute molecules is called semi permeable membrane. During osmosis and reverse osmosis, only solvent molecules move across the semi permeable membrane.

When gases are dissolved in water, it is accompanied by a release of heat energy, i.e., process is exothermic. When the temperature is increased, according to Lechatlier's Principle, the equilibrium shifts in backward direction, and thus gases becomes less soluble in liquids.

A substance dissolves in a solvent if the intermolecular interactions are similar in both the components.
For example: Polar solutes dissolve in polar solvents and non-polar solutes in non-polar solvents. Thus, we can say “like dissolves like”.

1. Reverse osmosis.
2. Fresh water container.
3. Cellulose acetate placed on a suitable support.
4. Desalination of sea water.

Among H, Cl, and F, H is least electronegative while F is most electronegative. Then, F can withdraw electrons towards itself more than Cl and H. Thus, trifluoroacetic acid can easily lose H + ions i.e., trifluoroacetic acid ionizes to the largest extent. Now, the more ions produced, the greater is the depression of the freezing point. Hence, the depression in the freezing point increases in the order:
Acetic acid < trichloroacetic acid < trifluoroacetic acid.

Egg in water will swell whereas in NaCl solution it will shrink. This is because due to osmosis, the net flow of solvent is from less concentrated to more concentrated solution.

Since both the components are appearing in the distillate and composition of liquid and vapour is same, this shows that liquids have formed azeotropic mixture and hence cannot be separated at this stage by distillation.