Which of the following statement(s) is/are correct?

Options

A. KOH is less strong alkali than NaOH
B. Milk of magnesia is an aqueous solution of `Mg(OH)_(2)`
C. `Mg^(+2)` ions are not precipitated with the addition of `NH_(4)OH` in the presence of `NH_(4)Cl`
D. `CaO_(2)` is less stable than `MgO_(2)`.

Answer

To determine which of the statements are correct, we will analyze each statement one by one.

### Step 1: Analyze the first statement: "KOH is less strong alkali than NaOH."

- **Explanation**: The strength of an alkali is related to its ionic character. As the size of the cation increases, the polarizing power decreases, leading to an increase in ionic character. K⁺ is larger than Na⁺, which means KOH is more ionic and thus a stronger alkali than NaOH. Therefore, this statement is **false**.

### Step 2: Analyze the second statement: "Milk of magnesia is an aqueous solution of Mg(OH)₂."

- **Explanation**: Milk of magnesia refers to a suspension of magnesium hydroxide (Mg(OH)₂) in water, not a true aqueous solution. It is turbid and not perfectly soluble. Hence, this statement is also **false**.

### Step 3: Analyze the third statement: "Mg²⁺ ions are not precipitated with the addition of NH₄OH in the presence of NH₄Cl."

- **Explanation**: When NH₄OH and NH₄Cl are added, the concentration of NH₄⁺ increases, which leads to a decrease in the concentration of OH⁻ ions due to the common ion effect. This results in a situation where the solubility product (Q) of Mg(OH)₂ is less than its solubility, preventing precipitation. Therefore, this statement is **true**.

### Step 4: Analyze the fourth statement: "CaO₂ is less stable than MgO₂."

- **Explanation**: The stability of peroxides increases down the group due to the increasing size of the cation, which decreases polarizing power and increases ionic character. Therefore, CaO₂ is more stable than MgO₂. This statement is **false**.

### Conclusion:
- The only correct statement is the third one: "Mg²⁺ ions are not precipitated with the addition of NH₄OH in the presence of NH₄Cl."

### Summary of the Correctness of Statements:
1. **False**: KOH is less strong alkali than NaOH.
2. **False**: Milk of magnesia is an aqueous solution of Mg(OH)₂.
3. **True**: Mg²⁺ ions are not precipitated with the addition of NH₄OH in the presence of NH₄Cl.
4. **False**: CaO₂ is less stable than MgO₂.