An advantage of detergent over soap is that detergents

Step 1: Analyze the question We need an advantage of detergents over soap. So the correct option must be a true benefit that soap lacks.

Step 2: Explain the concept

• Soap is the sodium or potassium salt of long-chain fatty acids. In hard water (containing Ca²⁺ and Mg²⁺ ions), it forms an insoluble scum: 2C₁₇H₃₅COONa + Ca²⁺ → (C₁₇H₃₅COO)₂Ca↓ + 2Na⁺ This wastes soap and prevents lathering.
• Detergents are usually sodium alkyl sulphonates or sulphates (soapless detergents). Their calcium and magnesium salts are soluble, so no scum forms and they lather readily even in hard water.

Step 3: Evaluate the options

• A. Readily available: Soap is also readily available, so this is not a real advantage.
• B. In powdered form: Soap can also be powdered or in bars, and this is not a chemical advantage.
• C. Non-biodegradable: This is a disadvantage. Many detergents (especially branched-chain ones) persist in the environment and cause water pollution and foaming in rivers.
• D. Lather readily with water: Correct. Detergents lather well in both soft and hard water, while soap does not lather readily in hard water.

Step 4: Answer

Tip: For soap vs. detergent questions, remember: soap makes scum in hard water, detergent doesn't. Also remember that non-biodegradability is a disadvantage of detergents, so it is a common trap option.