Pick out the incorrect statement.

Options

A. Mg also burns is gases such as `CO_(2)` and `SO_(2)`
B. Excess of `CO_(2)` when passed in lime- water turns it milky
C. `MgCl_(2).6H_(2)O` on heating hydrolyses to form MgO (magnesia), which is refractory
D. Alkaline - earth metals are denser and harder than alkali metals

Answer

To solve the question of identifying the incorrect statement, we will analyze each statement provided in the options.

### Step-by-Step Solution:

1. **Analyze Statement A**:
- The statement claims that Magnesium burns in gases such as Carbon Dioxide and Sulphur Dioxide.
- When Magnesium reacts with Carbon Dioxide, it forms Magnesium Oxide and Carbon.
- When it reacts with Sulphur Dioxide, it forms Magnesium Oxide and Sulphur.
- Therefore, this statement is **correct**.

2. **Analyze Statement B**:
- This statement claims that excess Carbon Dioxide passed through lime water turns it milky.
- Lime water is a dilute solution of Calcium Hydroxide (Ca(OH)₂).
- When Carbon Dioxide is passed through lime water, it reacts to form Calcium Carbonate (CaCO₃), which is insoluble in water and causes the milky appearance.
- However, if excess Carbon Dioxide is passed, it forms Calcium Bicarbonate (Ca(HCO₃)₂), which is soluble in water, thus removing the milkiness.
- Therefore, this statement is **incorrect**.

3. **Analyze Statement C**:
- The statement discusses the heating of Magnesium Chloride Hexahydrate (MgCl₂·6H₂O) leading to the formation of Magnesium Oxide (MgO), which is a refractory material.
- This statement is **correct** as Magnesium Oxide does indeed have refractory properties.

4. **Analyze Statement D**:
- This statement compares the densities and hardness of Alkaline Earth Metals (Group 2) with Alkali Metals (Group 1).
- Alkaline Earth Metals are indeed denser and harder than Alkali Metals due to their smaller ionic size and stronger metallic bonds.
- Therefore, this statement is **correct**.

### Conclusion:
- The incorrect statement is **Statement B**.

### Final Answer:
The incorrect statement is **Statement B**.

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