Which of the following statements (s) is/are not true about the diagonal relationship of `Be` and `Al`?

Options

A. Their oxides are basic
B. They become passive by conc `HNO_(3)`
C. Both react with `NaOH` to liberate hydrogen
D. Their carbides give acetlylene on hydrolysis

Explanation

To determine which statements about the diagonal relationship between Beryllium (Be) and Aluminium (Al) are not true, we will analyze each statement one by one based on their chemical properties.

### Step-by-Step Solution:

1. **Understanding Diagonal Relationship**:
- Beryllium (Be) and Aluminium (Al) are diagonally positioned in the periodic table, which leads to some similarities in their chemical properties due to comparable charge-to-radius ratios.

2. **Analyzing the Statements**:
- **Statement 1**: "Their oxides are basic."
- This statement is **not true**. The oxides of both Beryllium (BeO) and Aluminium (Al2O3) are amphoteric, meaning they can react with both acids and bases.
- **Example Reactions**:
- BeO + HCl → BeCl2 + H2O
- BeO + NaOH → Na2BeO2 + H2O
- Al2O3 + HCl → AlCl3 + H2O
- Al2O3 + NaOH → NaAlO2 + H2O
- Conclusion: Their oxides are not purely basic; they are amphoteric.

- **Statement 2**: "They become passive by concentrated HNO3."
- This statement is **true**. Both Be and Al form a protective oxide layer when treated with concentrated nitric acid (HNO3), which prevents further reaction.
- Conclusion: This statement is correct.

- **Statement 3**: "Both react with NaOH and liberate hydrogen."
- This statement is **true**. Both Beryllium and Aluminium react with sodium hydroxide (NaOH) to produce hydrogen gas.
- **Example Reactions**:
- Be + 2NaOH + 2H2O → Na2BeO2 + 2H2
- 2Al + 2NaOH + 6H2O → 2NaAl(OH)4 + 3H2
- Conclusion: This statement is correct.

- **Statement 4**: "Their carbides give acetylene on hydrolysis."
- This statement is **not true**. The hydrolysis of Beryllium carbide (Be2C) and Aluminium carbide (Al4C3) does not yield acetylene (C2H2). Instead, they produce methane (CH4).
- **Example Reactions**:
- Be2C + 4H2O → 2Be(OH)2 + CH4
- Al4C3 + 12H2O → 4Al(OH)3 + 3CH4
- Conclusion: This statement is incorrect.

3. **Final Conclusion**:
- The statements that are **not true** about the diagonal relationship of Be and Al are:
- Statement 1: "Their oxides are basic."
- Statement 4: "Their carbides give acetylene on hydrolysis."

### Summary of Incorrect Statements:
- **Statement 1**: Their oxides are basic. (Incorrect)
- **Statement 4**: Their carbides give acetylene on hydrolysis. (Incorrect)