1. Define the following terms: 1.1 homologous series 1.2 functional group (2) 2. Write down the structural formula of the functional group for the following homologous series: 2.1 alcohols 2.2 aldehydes (2) 2.3 carboxylic acids (2) 2.4 ketones (2) (2) [14]

Let's break down the problem step by step. ### 1. Definitions #### 1.1 Homologous Series A **homologous series** is a group of organic compounds that have the same functional group and similar chemical properties, but differ by a constant unit, typically a -CH₂- group. Members of a homologous series exhibit a gradual change in physical properties (such as boiling point and melting point) as the molecular size increases. #### 1.2 Functional Group A **functional group** is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that molecule. Functional groups determine the properties and reactions of organic compounds. Examples include hydroxyl (-OH), carbonyl (C=O), and carboxyl (-COOH) groups. ### 2. Structural Formulas of Functional Groups #### 2.1 Alcohols The functional group for alcohols is the **hydroxyl group** (-OH). The structural formula can be represented as: \[ \text{R-OH} \] where R represents an alkyl group. #### 2.2 Aldehydes The functional group for aldehydes is the **carbonyl group** (C=O) with a hydrogen atom attached to the carbon. The structural formula can be represented as: \[ \text{R-CHO} \] where R represents an alkyl group. #### 2.3 Carboxylic Acids The functional group for carboxylic acids is the **carboxyl group** (-COOH). The structural formula can be represented as: \[ \text{R-COOH} \] where R represents an alkyl group. #### 2.4 Ketones The functional group for ketones is also a **carbonyl group** (C=O), but it is flanked by two carbon atoms. The structural formula can be represented as: \[ \text{R-CO-R'} \] where R and R' represent alkyl groups. ### Summary of Answers 1.1 Homologous series: A group of organic compounds with the same functional group and differing by -CH₂-. 1.2 Functional group: A specific group of atoms responsible for the chemical reactions of a compound. 2.1 Alcohols: \(\text{R-OH}\) 2.2 Aldehydes: \(\text{R-CHO}\) 2.3 Carboxylic acids: \(\text{R-COOH}\) 2.4 Ketones: \(\text{R-CO-R'}\) This concludes the definitions and structural formulas for the specified terms.