MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

Hard water contains dissolved calcium and magnesium ions (Ca^ 2+ and Mg^ 2+ ). When soap (which is typically a sodium or potassium salt of a long-chain fatty acid, such as sodium stearate) is added to hard water, these ions react with the soap molecules. The sodium or potassium ions are replaced by calcium and magnesium ions, leading to the formation of insoluble calcium and magnesium salts of the fatty acids. For example: 2C_ 17 H_ 35 COONa + Ca^ 2+ (C_ 17 H_ 35 COO)_2Ca + 2Na^+ These insoluble precipitates separate out from the water and are commonly known as scum. Answer: Scum