Which one of the following contains all Lewis acids ?

Question

Question

This question was previously asked in

UPSC CDS-I 2025 (General Studies) Official Paper (Held On: 13 Apr, 2025)

Answer 1

The correct answer is Option 1.

Key Points

Lewis acids are chemical species that can accept an electron pair due to their electron-deficient nature.
Option 1 includes AlCl3, Co3+, and BF3, which are well-known Lewis acids:
- AlCl3: Aluminum chloride acts as a Lewis acid due to its incomplete octet and ability to accept electrons.
- Co3+: The cobalt ion (Co3+) is electron-deficient and readily accepts electron pairs.
- BF3: Boron trifluoride is a classical Lewis acid due to the electron deficiency of boron.
Other options contain species like NH3 and OH-, which are Lewis bases, or species like F- that are electron-rich and unable to act as Lewis acids.
Lewis acids play a critical role in many chemical reactions, such as catalysis and coordination chemistry.

Additional Information

Lewis Acid Definition:
- Named after G.N. Lewis, a Lewis acid is a chemical species that can accept a pair of electrons.
- This definition contrasts with Bronsted-Lowry acids, which are proton donors.
Examples of Lewis Acids:
- Common examples include BF3, AlCl3, Fe3+, and other electron-deficient compounds or metal ions.
- Transition metals in high oxidation states (e.g., Co3+) often act as Lewis acids.
Lewis Base:
- A Lewis base is the opposite of a Lewis acid—it donates an electron pair.
- Examples include NH3, OH-, and F-.
Applications of Lewis Acids:
- Used in catalysis, such as Friedel-Crafts reactions.
- Important in the formation of coordination complexes in inorganic chemistry.