Which of the following statements is/are correct ? 1. Detergents are cleaning agents which work both in hard water as well as ice- cold water. 2. Synthetic detergents are mainly classified into two categories: Anionic detergents and Cationic detergents.
Synthetic detergents are cleansing agents that have all the properties of soaps , but which actually do not contain any soap. These can be used both in soft and hard water as they give foam even in hard water. Some of the detergents give foam even in ice-cold water. Hence, Statement 1 is correct. Synthetic detergents are mainly classified into three categories: Anionic detergents, Cationic detergents, and Non-ionic detergents Hence, Statement 2 is incorrect. 1. Anionic Detergents: Anionic detergents are sodium salts of sulfonated long-chain alcohols or hydrocarbons. Alkyl hydrogen sulfates formed by treating long-chain alcohols with concentrated sulphuric acid are neutralized with alkali to form anionic detergents. Similarly, alkyl benzene sulphonates are obtained by neutralizing alkyl benzene sulphonic acids with alkali . In anionic detergents, the anionic part of the molecule is involved in the cleansing action . Sodium salts of alkyl benzene sulphonates are an important class of anionic detergents. They are mostly used for household work . Anionic detergents are also used in toothpaste . 2. Cationic Detergents: Cationic detergents are quarternary ammonium salts of amines with acetates, chlorides, or bromides as anions . The cationic part possesses a long hydrocarbon chain and a positive charge on the nitrogen atom . Hence, these are called cationic detergents. Cetyltrimethyl ammonium bromide is a popular cationic detergent and is used in hair conditioners. Cationic detergents have germicidal properties and are expensive , therefore, these are of limited use . 3. Non-ionic Detergents: Non-ionic detergents do not contain any ion in their constitution. One such detergent is formed when stearic acid reacts with polyethyleneglycol. Liquid dishwashing detergents are non-ionic types . The mechanism of cleansing action of this type of detergent is the same as that of soaps. These also remove grease and oil by micelle formation. The main problem that appears in the use of detergents is that if their hydrocarbon chain is highly branched, then bacteria cannot degrade this easily. Slow degradation of detergents leads to their accumulation. Effluents containing such detergents reach the rivers, ponds, etc. These persist in water even after sewage treatment and cause foaming in rivers, ponds, and streams, and their water gets polluted. These days the branching of the hydrocarbon chain is controlled and kept to the minimum . Unbranched chains can be biodegraded more easily and hence pollution is prevented