**Question:** Temporary and permanent hardness of water is removed by-

A. Calcium sulfate
B. Calcium carbonate
C. Calcium chloride
D. Calcium bicarbonate

**Core Concept:**

Water hardness refers to the presence of dissolved minerals, primarily calcium and magnesium ions, which can cause issues in daily life, such as scaling in pipes and appliances, and skin and hair problems. Temporary hardness results from the presence of bicarbonate ions, while permanent hardness is caused by carbonate and sulfate ions.

**Why the Correct Answer is Right:**

The correct answer is **B. Calcium carbonate** because it is responsible for permanent hardness in water. Calcium carbonate precipitates out of solution when water is heated, resulting in the removal of calcium and magnesium ions, which are the main contributors to water hardness.

**Why Each Wrong Option is Incorrect:**

**A. Calcium sulfate:** This is incorrect because it is responsible for gypsum formation, not water hardness. Calcium sulfate is a mineral that forms when water evaporates from saltwater pools or hot springs, not a contributor to water hardness.

**C. Calcium chloride:** This option is incorrect because calcium chloride is a salt used for de-icing roads and not a natural component of water hardness. It is not relevant to the removal of water hardness.

**D. Calcium bicarbonate:** Calcium bicarbonate is incorrect because it is responsible for temporary hardness, not permanent hardness. Bicarbonate ions (HCO3-) in water react with carbon dioxide to form carbonic acid (H2CO3), which dissociates into HCO3- and H+ ions, leaving behind calcium and magnesium ions causing temporary hardness.

**Clinical Pearl:**

Understanding the distinction between temporary and permanent water hardness is crucial for addressing water treatment and household issues. Temporary hardness is solved by heating the water, while permanent hardness requires treatment methods like water softening or lime removal systems to remove calcium and magnesium ions from the water.