MHTCET 18 Apr 2026 Shift 1 Paper

Concept:A Lewis acid is a species that accepts an electron pair to form a coordinate bond.Explanation:Beryllium belongs to group 2 and has the electronic configuration $1s^2 2s^2$.In $\mathrm{BeCl}_2$, the beryllium atom forms two covalent bonds with chlorine atoms using its two valence electrons.Thus, beryllium is surrounded by only $4$ electrons, giving it an incomplete octet.This electron-deficient beryllium atom can accept a lone pair of electrons from a Lewis base to complete its octet.Therefore, $\mathrm{BeCl}_2$ acts as a Lewis acid.In contrast, $\mathrm{BaCl}_2$, $\mathrm{KCl}$, and $\mathrm{LiCl}$ are primarily ionic salts, and their cations have stable noble gas configurations.These salts do not readily accept electron pairs and do not show Lewis acid behaviour.Hence, among the given options, only $\mathrm{BeCl}_2$ behaves as a Lewis acid.Answer:Option C: $\mathrm{BeCl}_2$