Moderate

Detergents are preferred over soaps for washing in hard water because:

Correct answer: C. Their calcium and magnesium salts are soluble in water

  • A. They are cheaper to produce
  • B. They are more environmentally friendly
  • C. Their calcium and magnesium salts are soluble in water
  • D. They are stronger bases

Explanation

Soaps react with the Ca²⁺ and Mg²⁺ ions present in hard water to form an insoluble precipitate known as scum. Detergents are synthetic surfactants that are designed so that their corresponding salts with these ions remain soluble, thus preventing scum formation and maintaining their cleaning ability.

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Industrial chemistry applies chemical reactions and material properties to the manufacture of adhesives, dyes and polymers. Coverage includes addition and condensation polymerisation, thermoplastics and thermosetting polymers, the structural basis of colour in dyes, and how adhesive composition enables bonding between surfaces.

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