Course Content
Section Name Topic Name 3 Classification of Elements and Periodicity in Properties 3.1 Why do we Need to Classify Elements ? 3.2 Genesis of Periodic Classification 3.3 Modern Periodic Law and the present form of the Periodic Table 3.4 Nomenclature of Elements with Atomic Numbers > 100 3.5 Electronic Configurations of Elements and the Periodic Table 3.6 Electronic Configurations and Types of Elements: s-, p-, d-, f – Blocks 3.7 Periodic Trends in Properties of Elements
Section Name Topic Name 7 Equilibrium 7.1 Equilibrium in Physical Processes 7.2 Equilibrium in Chemical Processes – Dynamic Equilibrium 7.3 Law of Chemical Equilibrium and Equilibrium Constant 7.4 Homogeneous Equilibria 7.5 Heterogeneous Equilibria 7.6 Applications of Equilibrium Constants 7.7 Relationship between Equilibrium Constant K, Reaction Quotient Q and Gibbs Energy G 7.8 Factors Affecting Equilibria 7.9 Ionic Equilibrium in Solution 7.10 Acids, Bases and Salts 7.11 Ionization of Acids and Bases 7.12 Buffer Solutions 7.13 Solubility Equilibria of Sparingly Soluble Salts
Section Name Topic Name 10 The s-Block Elements 10.1 Group 1 Elements: Alkali Metals 10.2 General Characteristics of the Compounds of the Alkali Metals 10.3 Anomalous Properties of Lithium 10.4 Some Important Compounds of Sodium 10.5 Biological Importance of Sodium and Potassium 10.6 Group 2 Elements : Alkaline Earth Metals 10.7 General Characteristics of Compounds of the Alkaline Earth Metals 10.8 Anomalous Behaviour of Beryllium 10.9 Some Important Compounds of Calcium 10.10 Biological Importance of Magnesium and Calcium
Section Name Topic Name 12 Organic Chemistry – Some Basic Principles and Techniques 12.1 General Introduction 12.2 Tetravalence of Carbon: Shapes of Organic Compounds 12.3 Structural Representations of Organic Compounds 12.4 Classification of Organic Compounds 12.5 Nomenclature of Organic Compounds 12.6 Isomerism 12.7 Fundamental Concepts in Organic Reaction Mechanism 12.8 Methods of Purification of Organic Compounds 12.9 Qualitative Analysis of Organic Compounds 12.10 Quantitative Analysis
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About Lesson

Methods of purification of organic compounds:

The various methods involved in the purification are:

  • Sublimation
  • Crystallisation
  • Distillation
  • Differential extraction
  • Chromatography

Sublimation: It is the process in which solid directly changes to gaseous form on heating and on cooling the gaseous state convert in to solid state.

The idea behind using this technique is to separate substance,that show sublimation from substance that do not sublime.

Crystallisation: This method is based on the difference in the solubility of compound and the impurities in the suitable solvent.

  • The impure compound in dissolved in a solvent in which it is sparingly soluble at room temperature, but appreciably soluble at higher temperature.
  • The solution is concentrated to get saturated solution.
  • On cooling the solution pure compound crystallizes out and is removed by filtration.
  • The filtrate contains impurities and small quantity of compound .

Distillation : This method is used to separate volatile liquids from non volatile impurities and also the liquids that have difference in their boiling points .

  • The liquids with different boiling point vaporise at different temperatures .Then these vapours are cooled and the liquids formed are collected separately.

Like chloroform and aniline can be easily separated by this technique as both have different boiling points.

For this technique:

(i) Take the mixture in a distillation flask. Fit the flask with a thermometer.

(ii) Arrange the apparatus as shown in the figure.

(iii) Heat the mixture slowly keeping a close watch at the thermometer and observe what happens.The vapours of one component with lower boiling point can be seen rising up in the distillation flask with the increase in temperature.

 (ii) These vapours get condensed in the condenser and can be collected (as pure liquid distillate) from the condenser outlet.

Fractional distillation: This method is used for those liquids which have nearly same boiling points that is the difference in their boiling point is not much .So, as they have same boiling points. Therefore ,liquids from both liquids condense and formed at same time.

  • In this technique ,vapours of liquid mixture are passed through a fractionating column before condensation .This fractionating column is fitted over round bottom flask.
  • Vapours of liquid with higher boiling point condense before the vapours of liquid with lower boiling point.
  • On reaching the top, the vapours become pure in low boiling component and passed through the condenser. The pure liquid is collected in receiver .Each successive condensation and vaporisation unit in the fractionating column is called theoretical plate. Example: separation of different components of crude oil

Distillation under reduced pressure: This method is used to purify liquids having very high boiling points and those which decompose at or below their boiling points.

  • Such liquids are made to boil at a temperature lower than their boiling points, by reducing the pressure on their surface. A liquid boils at a temperature, at which its vapour pressure is equal to external pressure .The pressure is reduced with the help of water pump. Example glycerol can be separated from spent-lye by this method

Steam distillation: This technique is applied to separate substances which are steam volatile and are immiscible in water.

  • In steam distillation steam from a steam generator is passed through a heated flask containing the liquid to be distilled.
  • The mixture of steam and the volatile organic compound is condensed and collected. Then compound is later separated from water using separating funnel.
  • In it the liquid boils ,when sum of vapour pressures due to organic liquid and due to water becomes equal to the atmospheric pressure.

 i.e. =P1 +p2

  • Since p1 is lower than p, the organic liquid vaporises at lower temperature than its boiling point.

Example: Aniline and water can be separated by this method

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