What is the result when soap is used in hard water?

Step-by-step solution

Hard water contains dissolved calcium and magnesium ions ( Ca²⁺ and Mg²⁺ ). 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: 2C₁₇H₃₅COONa + Ca²⁺ (C₁₇H₃₅COO)₂Ca + 2Na^+ These insoluble precipitates separate out from the wa