Question

Explain how soap cleans clothes. More amount of soap is required to clean
the clothes in hard water. Why?​

Answer 1

When soap is added to hard water, the Ca2+ and Mg2+ ions present in hard water react with soap. The sodium salts present in soaps are converted to their corresponding calcium and magnesium salts which are precipitated as scum. The insoluble scum sticks on the clothes and so the cleaning capacity of soap is reduced.