Question

Write notes on the following:
(a) Addition and substitution reactions
(b) Micelle
(c) Neutralization reaction

Hint:

In neutralization reactions, the acid and base cancel each other out, resulting in a neutral solution when mixed in the right proportions.

Answer 1

(a) Addition and Substitution Reactions:
- Addition Reaction: An addition reaction is a type of chemical reaction in which two or more molecules combine to form a single product. In this reaction, a molecule adds across a double or triple bond in an organic compound. For example, the addition of hydrogen to an alkene in the presence of a catalyst results in an alkane. \[ \text{C}_2\text{H}_4 + \text{H}_2 \xrightarrow{\text{Ni}} \text{C}_2\text{H}_6 \] - Substitution Reaction: In a substitution reaction, one atom or group of atoms in a molecule is replaced by another atom or group of atoms. A common example of substitution is the halogenation of alkanes. For example, when chlorine reacts with methane, hydrogen is replaced by chlorine: \[ \text{CH}_4 + \text{Cl}_2 \rightarrow \text{CH}_3\text{Cl} + \text{HCl} \]
(b) Micelle:
A micelle is an aggregate of surfactant molecules in a liquid, such as water, where the hydrophobic (water-repelling) tails of the surfactant molecules are inward and the hydrophilic (water-attracting) heads are on the outside. Micelles are important in the emulsification of oils in water, where they allow the dispersion of non-polar substances in polar solvents. They play a critical role in soap and detergent actions by trapping oil or grease in the center.
(c) Neutralization Reaction:
A neutralization reaction occurs when an acid reacts with a base to form salt and water. The general form of the reaction is: \[ \text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water} \] For example, when hydrochloric acid reacts with sodium hydroxide, the result is the formation of sodium chloride and water: \[ \text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O} \] This reaction is an important process in many biological and chemical systems and is used in titration to determine the concentration of an acid or base.
Conclusion:
1. Addition reactions involve the combination of molecules, while substitution reactions involve the replacement of atoms or groups in a molecule.
2. Micelles are formed by surfactants and are used to emulsify oils in water.
3. A neutralization reaction involves the reaction between an acid and a base to form a salt and water.