Question

The incorrect statement from the following is

• A. Aluminium dissolves in conc. HNO$_3$ and liberates H$_2$ gas
• B. Borazole contains 12$\sigma$ and 3$\pi$ bonds
• C. Gallium oxide is amphoteric in nature
• D. BF$_3$ is a Lewis acid

Hint:

Passivation prevents some metals like aluminium from reacting with oxidizing acids like HNO$_3$ due to formation of an inert oxide layer.

Answer 1

The Correct Option is A

Step 1: Examine Aluminium's reaction with concentrated HNO$_3$
Aluminium forms a passive oxide layer (Al$_2$O$_3$) in concentrated nitric acid due to strong oxidizing nature of HNO$_3$, preventing further reaction. So, it does not liberate hydrogen gas.
Hence, Statement 1 is incorrect. Step 2: Analyze Borazole bonding
Borazole (B$_3$N$_3$H$_6$) has a structure similar to benzene and contains 12 $\sigma$ bonds (6 B–N, 3 B–H, and 3 N–H) and 3 $\pi$ bonds (due to resonance).
So, Statement 2 is correct. Step 3: Amphoteric nature of Ga$_2$O$_3$
Gallium oxide reacts with both acids and bases, confirming its amphoteric nature.
So, Statement 3 is correct. Step 4: BF$_3$ as Lewis acid
Boron trifluoride is an electron-deficient compound and readily accepts a lone pair, making it a classic Lewis acid.
So, Statement 4 is correct.