Question

Water is well known amphoprotic solvent. In which chemical reaction water is behaving as a base ?

• A. $ H_2SO_4 + H_2O \longrightarrow H_3O^+ + HSO_4^- $
• B. $ H_2O + H_2O \longrightarrow H_3O^+ + OH^- $
• C. $ H_2O + NH_2^- \longrightarrow NH_3^+ + OH^- $
• D. $ H_2O + NH_3 \longrightarrow NH^+_4 + OH^- $

Answer 1

Answer: (A)

According to Bronsted-Lowry concept, bases are the substance which have a tendency to accept a proton.

(a) $\underset{\text{acid}}{H _{2} SO _{4}}+ \underset{\text{base}}{H _{2} O} \rightarrow \underset{\text{conjugated acid}}{H _{3} O ^{+}}+ \underset{\text{conjugated base}}{HSO _{4}^{-}}$

(b) $\underset{\text{acid}}{H _{2} O} + \underset{\text{base}}{H _{2} O} \longrightarrow \underset{\text{conjugate acid}}{H _{3} O ^{+}}+ \underset{\text{conjugate base}}{OH ^{-}}$

(c) $\underset{\text{acid}}{H _{2} O} + \underset{\text{base}}{NH _{2}^{-}} \longrightarrow \underset{\text{conjugate acid}}{NH _{3}}+ \underset{\text{conjugate base}}{OH ^{-}}$

(d) $\underset{\text{acid}}{H _{2} O }+ \underset{\text{base}}{NH _{3}} \longrightarrow \underset{\text{conjugate acid}}{NH _{4}^{+}}+ \underset{\text{conjugate base}}{OH ^{-}}$