In Clark's method the chemical used to remove hardness of water us

Options

A. `Na_2CO_3`
B. `Ca(OH)_2`
C. NaOH
D. `CaCO_3`

Answer

To solve the question regarding Clark's method for removing hardness of water, we can follow these steps:

### Step 1: Understand the Context
Clark's method is a process used to remove temporary hardness from water. Temporary hardness is primarily caused by the presence of bicarbonate ions (HCO3-) in the water.

**Hint:** Temporary hardness can be removed by heating or by adding specific chemicals.

### Step 2: Identify the Chemical Used
In Clark's method, the chemical used to remove hardness is calcium hydroxide (Ca(OH)2). This compound reacts with the bicarbonate ions present in the water.

**Hint:** Look for a chemical that can react with bicarbonate ions to form a precipitate.

### Step 3: Reaction Mechanism
When calcium hydroxide is added to water containing bicarbonate ions, it reacts to form calcium carbonate (CaCO3), which is insoluble and precipitates out of the solution. The reaction can be represented as follows:

\[ \text{Ca(OH)}_2 + 2 \text{HCO}_3^- \rightarrow \text{CaCO}_3 \downarrow + 2 \text{H}_2\text{O} \]

This shows that calcium carbonate precipitates out, effectively removing the hardness from the water.

**Hint:** Remember that the formation of a precipitate indicates the removal of hardness.

### Step 4: Conclusion
Thus, the chemical used in Clark's method to remove hardness of water is calcium hydroxide.

**Final Answer:** Calcium hydroxide (Ca(OH)2) is the chemical used in Clark's method to remove hardness of water.