Which of the following statements is incorrect?

Options

A. `NaHCO_(3)` on heating gives `Na_(2)CO_(3)`
B. Pure sodium metal dissolves in liquid ammonia to give blue solution.
C. NaOH reacts with glass to give sodium silicate
D. Aluminium reacts with excess NaOH to give `Al(OH)_(3)`

Explanation

To determine which statement is incorrect, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: NaHCO3 on heating gives Na2CO3.**
- When sodium bicarbonate (NaHCO3) is heated, it decomposes to form sodium carbonate (Na2CO3), water (H2O), and carbon dioxide (CO2).
- The balanced reaction is:
\[ 2 \text{NaHCO}_3 \rightarrow \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} + \text{CO}_2 \]
- This statement is **correct**.

2. **Statement 2: Pure sodium metal dissolves in liquid ammonia to give a blue solution.**
- When sodium metal is dissolved in liquid ammonia, it forms solvated electrons which give the solution a characteristic blue color.
- The reaction can be represented as:
\[ \text{Na} \rightarrow \text{Na}^+ + e^- \text{ (solvated)} \]
- The blue color is due to these solvated electrons. Thus, this statement is **correct**.

3. **Statement 3: NaOH reacts with glass to give sodium silicate.**
- Glass is primarily composed of silicon dioxide (SiO2). When NaOH reacts with SiO2, it forms sodium silicate (Na2SiO3).
- The balanced reaction is:
\[ \text{SiO}_2 + 2 \text{NaOH} \rightarrow \text{Na}_2\text{SiO}_3 + \text{H}_2\text{O} \]
- This statement is **correct**.

4. **Statement 4: Aluminium reacts with excess NaOH to give Al(OH)3.**
- When aluminum reacts with excess sodium hydroxide (NaOH) in the presence of water, it forms sodium aluminate (NaAlO2) and hydrogen gas (H2), not aluminum hydroxide (Al(OH)3).
- The balanced reaction is:
\[ 2 \text{Al} + 2 \text{NaOH} + 6 \text{H}_2\text{O} \rightarrow 2 \text{NaAl(OH)}_4 + 3 \text{H}_2 \]
- Therefore, this statement is **incorrect**.

### Conclusion:
The incorrect statement is **Statement 4: Aluminium reacts with excess NaOH to give Al(OH)3**.