Selecte the correct statement.

Options

A. O-H bond is stronger than O-D bond
B. O-H bond is weaker than O-D bond
C. Permanent hardness of water is due to the presence of bicarbonates of calcium and magnesium
D. O-H and O-D bond strenght is same

Answer

To solve the question "Select the correct statement," we will analyze the statements provided and determine their validity step by step.

### Step 1: Analyze the First Statement
The first statement claims that the bond of OH (hydroxyl) is stronger than OD (deuterium oxide or heavy water).

- **Understanding Bonds**: The bond strength can be influenced by the mass of the atoms involved. In this case, we have hydrogen (mass number 1) in OH and deuterium (mass number 2) in OD.
- **Electronegativity**: Hydrogen is more electronegative than deuterium. This means that the bond in OH is more polar, leading to a greater ability of oxygen to attract the bonding electrons towards itself.
- **Bond Strength**: A more polar bond (like OH) is typically easier to break due to the greater electron density around the electronegative atom, making it a weaker bond compared to OD.

**Conclusion**: The first statement is incorrect. The bond of OH is weaker than OD.

### Step 2: Analyze the Third Statement
The third statement discusses the causes of permanent hardness in water, stating it is due to the presence of bicarbonate of calcium and magnesium.

- **Types of Hardness**: There are two types of hardness in water: temporary and permanent. Temporary hardness is primarily due to bicarbonates, which can be removed by boiling. Permanent hardness, however, is due to the presence of calcium and magnesium salts, such as sulfates and chlorides.
- **Correctness of the Statement**: The statement incorrectly attributes permanent hardness to bicarbonates. Bicarbonates are responsible for temporary hardness.

**Conclusion**: The third statement is also incorrect.

### Final Conclusion
Since both analyzed statements (the first and third) are incorrect, we conclude that the correct answer is that the first statement is wrong, and the second statement (not provided in the transcript) must be correct if it exists.

### Summary of the Solution
- The bond of OH is weaker than OD (first statement is incorrect).
- Permanent hardness is not due to the presence of bicarbonate of calcium and magnesium (third statement is incorrect).