Which of the following incorrect :

Options

A. Ionic product `D_(2)OgtH_(2)O`
B. Solubility of inorganic substances `H_(2)OgtD_(2)O`
C. Mass `D_(2)OgtH_(2)O`
D. Heat of fusion `D_(2)OgtH_(2)O`

Answer

To determine which of the statements regarding heavy water (D2O) and regular water (H2O) is incorrect, we will analyze each statement step by step.

### Step 1: Analyze the Ionic Product of D2O and H2O
- The ionic product refers to the equilibrium constant for the dissociation of water into ions. For H2O, the dissociation can be represented as:
\[ H_2O \rightleftharpoons H^+ + OH^- \]
- For D2O, the dissociation is:
\[ D_2O \rightleftharpoons D^+ + OD^- \]
- The bond strength in D2O (O-D bond) is stronger than that in H2O (O-H bond). Therefore, D2O will dissociate less than H2O, resulting in a lower ionic product for D2O compared to H2O.

**Conclusion for Step 1:** The statement that the ionic product of D2O is greater than that of H2O is incorrect.

### Step 2: Analyze the Solubility of Inorganic Substances
- It is known that water (H2O) has a higher dielectric constant than heavy water (D2O). A higher dielectric constant enhances the solubility of ionic compounds in the solvent.
- Therefore, inorganic substances are generally more soluble in H2O than in D2O.

**Conclusion for Step 2:** The statement that the solubility of inorganic substances is more in water than in heavy water is correct.

### Step 3: Compare the Mass of Heavy Water and Water
- The molecular mass of H2O is approximately 18 g/mol, while the molecular mass of D2O is approximately 20 g/mol (since deuterium has double the mass of hydrogen).
- Thus, the mass of heavy water is indeed greater than that of regular water.

**Conclusion for Step 3:** The statement that the mass of heavy water is greater than that of water is correct.

### Step 4: Analyze the Heat of Fusion
- The heat of fusion is the amount of energy required to change a substance from solid to liquid at its melting point.
- Since the O-D bond in D2O is stronger than the O-H bond in H2O, it requires more energy to break these bonds in D2O. Therefore, the heat of fusion for D2O is greater than that for H2O.

**Conclusion for Step 4:** The statement that the heat of fusion is more for heavy water than for water is correct.

### Final Conclusion
After analyzing all the statements:
- The incorrect statement is: "The ionic product of D2O is greater than that of H2O."

Thus, the answer is that the first statement is incorrect.