Question

Give the reaction for formation of scum with hard water

Answer 1

✴ Soaps are sodium or potassium salts of higher fatty acids. Hardness in water is due to the presence of Ca^2+ and Mg^2+ ions, present as their salts. The soap first reacts with calcium abd magnesium ions to form insoluble precipitate of calcium and magnesium salts of fatty acids which float as an off- white layer over wated. This layer is called scum.




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Answer 2

When soap is used for washing the clothes with hard water,very large amount of soap molecules is wasted in reacting with calcium and magnesium ions of hard water to form scum

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