Question

Soaps do not work in hard water containing calcium and magnesium ions because

• A. $Ca^{2 +}$ and $Mg^{2 +}$ ions form insoluble calcium and magnesium salts in the form of scum
• B. $Na^{+}$ and $K^{+}$ present in soap react with $Ca^{2 +}$ and $Mg^{+}$ and hinder cleansing process
• C. a large amount of soap is to be used in presence of $Ca^{+}$ and $Mg^{+}$
• D. scum formed by combination of $Na^{+}$ , $Ca^{2 +}$ and $Mg^{2 +}$ stick to the cloth and are not removed on agitation

Answer 1

Answer: (A)

$Ca^{2 +}$ and $Mg^{2 +}$ ions form insoluble calcium and magnesium soaps respectively when sodium or potassium soaps are dissolved in hard water.



These insoluble soaps separate as scum in water and are useless as cleansing agent.