CHAPTER 1- SOLUTIONS
1) Distinguish between molarity and molality
- Molarity ~ number of moles of solute dissolved per liter of the solution
FORMULA [M=WB x 1000 / MB x V(ML)]
- Molality ~ number of moles of solute dissolved in 1kg of solvent
FORMULA [M=WB x 1000 / MB x WA(G)]
2) State and explain Henry's law?
- Henry’s law states that at constant temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas. Mathematically, p = KH.χ (where p is the partial pressure, χ is the mole fraction and KH is the Henry’s law constant).
3) What are the important applications of Henry’s Law?
- (i) In the preparation of soda water and soft drinks (ii) A medical condition known as Bends in Scuba divers
4) what are colligative properties?
- These are properties which depend only on the number of solute particles and not on their nature. The important colligative properties are (i) Relative lowering of vapour pressure (ii) Elevation of boiling point (iii) Depression of freezing point (iv) Osmotic pressure
What is osmotic pressure?
- : It is the excess pressure that must be applied on the solution side to prevent osmosis.
5) What is reverse osmosis? Write any one of its applications.
- It is the process of flow of solvent molecules from solution side to solvent side through a semipermeable membrane (SPM), when a pressure greater than osmotic pressure is applied on the solution side. [OR, If a pressure larger than the osmotic pressure is applied to the solution side, the direction of osmosis gets reversed]. It is used in desalination of sea water OR in water purification.
6) What are isotonic solutions? Give an example
- Two solutions having the same osmotic pressure are called isotonic solutions. E.g. 0.9% (mass/volume) NaCl solution and our blood cells.
7) What are azeotropes?
- They are constant boiling mixtures and have the same composition in liquid and vapour phases.
8) Explain the different types of azeotropes?
- There are 2 types of azeotropes: Minimum boiling azeotropes: Formed by solutions which show large positive deviation from Raoult’s law. E.g. 95% aqueous solution of ethanol by volume. Maximum boiling azeotrope: Formed by solutions which show large negative deviation from Raoult’s law. E.g. 68% aqueous solution of HNO3 by mass
Raoult's Law Graph
Adjust the pure vapor pressures below and click "Update Graph" to see how the total vapor pressure and partial pressures change with composition.