Statement about heavy water are given below .
A. Heavy water is used in exchange reactions for the study of reaction mechanisms.
B. Heavy water is prepared by exhaustive electrolysis of water
C. Heavy water has higher boiling point than ordinary water.
D. Viscosity of `H_2 O` is greater than `D_2 O `

Options

A. A, B and C only
B. A and B only
C. A and D only
D. A and C only

Answer

To determine which statements about heavy water (D₂O) are correct, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** Heavy water is used in exchange reactions for the study of reaction mechanisms.

**Analysis:**
Heavy water is indeed used in various chemical reactions, especially in kinetic studies where the isotope effect can provide insights into the mechanism of the reaction. The presence of deuterium (D) instead of hydrogen (H) can alter reaction rates and help in understanding reaction pathways.

**Conclusion:** Statement A is correct.

### Step 2: Analyze Statement B
**Statement B:** Heavy water is prepared by exhaustive electrolysis of water.

**Analysis:**
Heavy water can be prepared by exhaustive electrolysis of water, where the lighter hydrogen isotopes are preferentially removed, leading to an enrichment of deuterium in the remaining water. This method is a well-known technique for producing heavy water.

**Conclusion:** Statement B is correct.

### Step 3: Analyze Statement C
**Statement C:** Heavy water has a higher boiling point than ordinary water.

**Analysis:**
The boiling point of heavy water (D₂O) is indeed higher than that of ordinary water (H₂O). The boiling point of D₂O is approximately 101.4°C, while that of H₂O is 100°C. This difference is due to the stronger hydrogen bonding in heavy water, which results from the presence of deuterium.

**Conclusion:** Statement C is correct.

### Step 4: Analyze Statement D
**Statement D:** Viscosity of H₂O is greater than D₂O.

**Analysis:**
The viscosity of heavy water (D₂O) is actually greater than that of ordinary water (H₂O). The viscosity of H₂O is about 0.8903 centipoise, while that of D₂O is approximately 1.107 centipoise. This means that heavy water is more viscous than ordinary water.

**Conclusion:** Statement D is incorrect.

### Final Conclusion
The correct statements regarding heavy water are A, B, and C. The only incorrect statement is D.

### Summary of Correct Statements
- A: Correct
- B: Correct
- C: Correct
- D: Incorrect