Ch 11 Chemistry Class 11 Notes

• Define Order of Reaction and its importance: The order of reaction is given by the sum of all the exponents to which the concentrations in the rate equation are raised. OR The order of reaction may also be defined as the number of reacting molecules, whose concentrations alter as a result of the chemical change. Importance 1. The order of reaction provides valuable information about the mechanism of a reaction. 2. The order of a reaction is an experimentally determined quantity and cannot be inferred simply by looking at the reaction equation. 3. The sum of the exponents in the rate equation may or may not be the same as in a balanced chemical equation. 4. The chemical reactions are classified as zero, first, second and third order reactions.
• Explanation with Examples
• Decomposition of nitrogen pentoxide: Decomposition of nitrogen pentoxide involves the following equation.
• Hydrolysis of tertiary butyl bromide
• Oxidation of nitric oxide
• Reaction of ferric chloride and potassium iodide
• Formation of carbon tetrachloride from chloroform
• Definition of Half Life Period with examples
• Determination of the Rate of a Chemical Reaction: 1. After some time, a sample of reaction mixture is withdrawn by a pipette and run into about four times its volume of ice cold water. 2. The dilution and chilling stops the reaction. 3. The acid formed is titrated against a standard alkali, say NaOH. 4. Phenolphthalein is used as an indicator. 5. The analysis is repeated at various time intervals after the start of reaction to get information about the change in concentration of acetic acid formed during the reaction at different time intervals. 6. The different concentrations of acetic acid are plotted against the time. 7. A rising curve is obtained.
• Measurement of Rate of Reaction
• Physical Methods (i) Spectrometry (ii) Electrical Conductivity Method
• What is Chemical Method with example
• Determination of Rate of Reaction
• Finding the Order of Reaction: Following methods are used to determine the order of reaction. 1. Method of hit and trial 2. Graphical method 3. Differential method 4. Half life method 5. Method of large excess Half Life Method Half life of a reaction is inversely proportional to the initial concentration of reactants raised to the power one less than the order of reaction. 
• Half Life Method with Mathematical Expression
• Factors Affecting Rates of Reactions: Some of the important factors affecting rates of reactions are given below: 1. Nature of Reactants The rate of reaction depends upon the nature of reacting substances. Electronic configuration The chemical reactivity of the substances is controlled by their electronic configuration. Example The elements of I-A group have one electron in their outermost s-orbital. They react with water more swiftly than those of II-A group elements having two electrons in their outermost s-orbital. Type of reactions The neutralization and double decomposition reactions are very fast as compared to those reactions in which bonds are rearranged. Oxidation-reduction reactions involve the transfer of electrons and are slower than ionic reactions.
• Determination of energy of activation
• Definition of catalysis
• Definition of catalyst
• Types of Catalysis Following are the two types of catalysis: 1. Homogeneous catalysis 2. Heterogeneous catalysis
• Characteristics of a Catalyst
• Catalyst remains unchanged with example
• Needed in small amounts with example
• Explain Enzyme Catalysis with examples
• Characteristics of Enzyme Catalysis