Question

Which equilibrium can be described as an acid-base reaction using the Lewis acid-base definition, but not using Bronsted-Lowry definition?

• A. $NH_{3}+CH_{3}COOH\rightleftharpoons CH_{3}COO^{-}+NH_{4}^{+}$
• B. $H_{2}O+CH_{3}COOH\rightleftharpoons H_{3}O^{+}+CH_{3}COO^{-}$
• C. $4 NH _{3}+\left[ Cu \left( H _{2} O \right)_{4}\right]^{2+} \rightleftharpoons\left[ Cu \left( NH _{3}\right)_{4}\right]^{2+}+4 H _{2} O$
• D. $2NH_{3}+H_{2}SO_{4}\rightleftharpoons2NH_{4}^{+}+SO_{4}^{2 -}$

Answer 1

Answer: (C)

According to Lewis acid-base concept, bases are electron pair donor and acids are electron pair acceptor. In reaction

$4 NH _{3}+\left[ Cu \left( H _{2} O \right)_{4}\right]^{2+} \rightleftharpoons\left[ Cu \left( NH _{3}\right)_{4}\right]^{2+}+4 H _{2} O$

$NH_{3}$ molecules donates electron pairs, so it is a Lewis base and $Cu^{2 +}$ accepts the electron pairs donated by the $NH_{3}$ molecules, so it acts as Lewis acid.