Which of the following is not correct for `D_2 O` ?

Options

A. Boiling point is higher than `H_2O`
B. `D_2O` reacts slowly than `H_2O`
C. Viscosity is higher than `H_2O ` at `25^@` C
D. Solubility of NaCl in it is more than `H_2O`

Answer

To determine which statement is not correct regarding D₂O (heavy water), we need to analyze the properties of D₂O compared to H₂O (regular water). Here’s a step-by-step breakdown:

### Step 1: Understand the properties of D₂O
D₂O, or heavy water, consists of deuterium (D), which is an isotope of hydrogen. This gives D₂O different physical and chemical properties compared to H₂O.

### Step 2: Analyze the boiling point
D₂O has a higher boiling point than H₂O. This is due to the stronger hydrogen bonds formed in D₂O because of the presence of deuterium. Therefore, the statement regarding the boiling point being higher is correct.

### Step 3: Examine the reactivity
D₂O reacts more slowly than H₂O in many chemical reactions. This is because the O-D bond is stronger than the O-H bond, making it less reactive. Thus, the statement that D₂O reacts slowly compared to H₂O is also correct.

### Step 4: Investigate viscosity
The viscosity of D₂O is indeed higher than that of H₂O at 25 degrees Celsius. This is due to the stronger intermolecular forces in D₂O. Therefore, the statement regarding viscosity being higher is correct as well.

### Step 5: Check the solubility of NaCl
The solubility of NaCl in D₂O is less than in H₂O. This is because the stronger O-D bonds in D₂O make it less effective at solvating ions compared to H₂O. Therefore, the statement that NaCl is more soluble in D₂O than in H₂O is incorrect.

### Conclusion
The statement that is not correct for D₂O is that "the solubility of NaCl in D₂O is more than in H₂O."

### Summary of the Solution
1. D₂O has a higher boiling point than H₂O (correct).
2. D₂O reacts more slowly than H₂O (correct).
3. The viscosity of D₂O is higher than that of H₂O (correct).
4. The solubility of NaCl in D₂O is less than in H₂O (not correct).