Solution

• Solutions are homogeneous mixtures containing two or more components.
• The component that is present in larger quantity in a solution is called solvent.
• Solvent determines the physical state of the solution.
• One or more components present in the solution other than solvent are called solutes.
• Solutions containing only two components are called binary solutions.
• Each component in a binary solution may be solid, liquid or gaseous.
• Relative lowering of vapour pressure, ∆P = i x w 2 x M 1 P 1 0 w 1 x M 2 2
• Elevation of Boiling point (∆T b ) = i.K b .m 3
• Depression of freezing point (∆T f ) = i.K f .m 4
• Osmotic Pressure (π) = i.CRT
• Based on their physical states, solutions can be of the following types: gaseous, liquid, and solid.
• Gaseous solutions can be a mixture of O2 and CO2, or a gas like chloroform mixed with nitrogen gas, or water vapour in air.
• Liquid solutions can be oxygen dissolved in water, soda water, alcohol dissolved in water, dilute acids and alkalies, or salt in water, glucose in water.
• Solid solutions can be hydrogen in Pd, Pt, Ni, amalgam of mercury with sodium, gold ornaments, alloys of metals.
• Composition of a solution can be expressed in terms of concentration.
• Concentration is defined as the number of moles of solute present per litre of the solution.
• Concentration of a solution can be expressed by the following ways: mass percentage (w/w), volume percentage (v/v), mass by volume percentage (w/v), and parts per million (ppm).
• According to Dalton’s law of partial pressures, the total pressure (p total) in a solution is the sum of the partial pressures of the components of the solution.
• Raoult’s Law can be considered as a special case of Henry’s Law, where p 1 = χ 1 p 1 0.
• Condensation is a process where water vapour changes into water droplets.
• According to Raoult’s law, for a solution of volatile liquids, the partial vapour pressure of each component in the solution is directly proportional to its mole fraction.
• The composition of vapour phase in equilibrium with the solution is determined from the partial pressures of the components.
• As the temperature increases, the vapour pressure also increases.
• Based on the volatility of the solute, the vapour pressure of the solution is greater or less than that of the solvent.
• If y 1 and y 2 are the mole fractions of the components 1 and 2 respectively in the vapour phase, then using Dalton’s law of partial pressures: p 1 = y 1 p total and p 2 = y 2 p total.
• Raoult’s Law, a quantitative relationship between the vapour pressure and mole fraction of solute in a solution, was first given by a French chemist F.M Raoult.
• The liquid solvent is generally volatile, while the solute may or may not be volatile.
• According to Henry’s law, solubility of a gas in a liquid is given by p = K H χ.
• Vapour pressure is the pressure exerted by the vapour in equilibrium with its own liquid, which depends on the nature of the liquid and the temperature.
• Dalton’s law of partial pressures states that the total pressure (p total) in a solution is the sum of the partial pressures of the components of the solution.
• In liquid solutions, the solvent is always a liquid and the solute can be a gas, a liquid or a solid.
• For dilute solutions, the elevation of boiling point is directly proportional to molality (m), i.e. ∆T b α m or ∆T b = K b .m.
• The Boiling Point Elevation Constant (K b ) is defined as the elevation of boiling point for 1 molal solution, i.e. it is the increase in boiling point of a solution containing 1 mol of a solute in 1 kg of the solvent.
• The elevation of boiling point (∆T b ) is calculated as ∆T b = T b - T b 0.
• For water, K b = 0.52K kg/mol.
• The molar mass of an unknown solute can be calculated using the equation ∆T b = 1000K b .w 2 w 1 .M 2.
• The relative lowering of vapour pressure (∆ p / p 1 0 ) is calculated as ∆ p / p 1 0 - 1.
• The lowering of vapour pressure of the solvent (∆ p ) is calculated as p 1 0 - p 1.
• The mole fraction of the solute (x 2 ) is calculated as p 1 0 /(p 1 0 - p 1).
• The molality (m) of a solution is calculated as w 2 /M 2 p 1 0 w 1 /M 1.