NDA General Ability Question (2026) — Solution

Step-by-step solution

Lewis acids are chemical species that can accept a pair of electrons. They are typically electron-deficient molecules or cations with empty orbitals. AlCl _3 has an incomplete octet (6 electrons around Al) and acts as a Lewis acid. NH _3 has a lone pair of electrons on the nitrogen atom and acts as a Lewis base (electron pair donor). BF _3 has an incomplete octet (6 electrons around B) and acts as a Lewis acid. FeCl _3 has empty d-orbitals on the central iron atom, allowing it to accept electron pairs, thus acting as a Lewis acid. Therefore, AlCl _3, BF _3, and FeCl _3 are Lewis acids. There are three Lewis acids in the given list. Answer: Three