Question

Which one of the following statement is NOT correct for detergents?
1. Have all properties of soaps
2. Can be used in soft and hard water
3. Cannot be used in acidic medium
4. Generally obtained from vegetable oil

Answer 1

Correct Answer - Option 3 : Cannot be used in acidic medium

The correct answer is Cannot be used in acidic medium.

Detergents

• Detergents are cleaning agents and can be classified into the following two categories:
  • Soaps
  • Synthetic detergents
• The synthetic detergents do not contain any soap but have all the properties of soaps.
• Unlike soaps, synthetic detergents give foam even in hard water, thus can be used both in soft and hard water. Some of the detergents have the property of giving foam even in ice-cold water.
• Unlike soaps, synthetic detergents can also be used in an acidic medium, while soaps get precipitated in the acidic medium.

The synthetic detergents are of the following three types:

• Anionic detergents - these are sodium salts of sulfonated long-chain alcohols or hydrocarbons. The anionic part of the molecule is involved in the cleansing action. eg: Sodium lauryl sulfate, Sodium dodecylbenzene sulphonate, etc.
• Cationic detergents - these are quarternary ammonium salts of amines with acetates, chlorides, or bromides as anions. Cetyltrimethylammonium bromide is a popular cationic detergent and is used in hair conditioners.
• Non-ionic detergents - these Non-ionic detergents do not contain any ion in their constitution. These are obtained from vegetable oil, for example, one such detergent is formed when stearic acid reacts with polyethyleneglycol.

Uses

• Anionic detergents are mostly used for household work and are also used in toothpaste.
• Cationic detergents are used in making germicidal.
• Non-ionic detergents are used as liquid dishwashing detergents.

Environmental effect -

• Detergents containing highly branched hydrocarbon chains cannot be easily degraded by bacteria. 
• These persist in water even after sewage treatment and cause foaming in rivers, ponds, and streams; and their water gets polluted.