Question

use the following information to answer the next question.
the hydrogen carbonate ion, hco₃⁻, may act as an acid or a base in aqueous solution.

1. the equation shown below where hydrogen carbonate is acting as an acid is

hco₃⁻(aq) + h₂o(l) ⇌ co₃²⁻(aq) + h₃o⁺(aq)
hco₃⁻(aq) + h₃o⁺(aq) ⇌ h₂co₃(aq) + h₂o(l)
hco₃⁻(aq) + oh⁻(aq) ⇌ h₂co₃(aq) + o²⁻(aq)
hco₃⁻(aq) + h₂o(l) ⇌ h₂co₃(aq) + oh⁻(aq)

Explanation:

Step1: Recall the definition of an acid

An acid donates a proton (\(H^+\)).

Step2: Analyze each equation

• For \(HCO_3^-(aq)+H_2O(l)

ightleftharpoons CO_3^{2 - }(aq)+H_3O^+(aq)\): \(HCO_3^-\) donates a proton (\(H^+\)) to \(H_2O\) to form \(CO_3^{2 - }\) and \(H_3O^+\).

• For \(HCO_3^-(aq)+H_3O^+(aq)

ightleftharpoons H_2CO_3(aq)+H_2O(l)\): \(HCO_3^-\) accepts a proton (\(H^+\)) from \(H_3O^+\), so it acts as a base.

• For \(HCO_3^-(aq)+OH^-(aq)

ightleftharpoons H_2CO_3(aq)+O^{2 - }(aq)\): \(HCO_3^-\) accepts a proton (\(H^+\)) (as \(OH^-\) can be thought of as a proton - acceptor in this context in terms of acid - base reaction where \(HCO_3^-\) gains \(H^+\) to form \(H_2CO_3\)), so it acts as a base.

• For \(HCO_3^-(aq)+H_2O(l)

ightleftharpoons H_2CO_3(aq)+OH^-(aq)\): \(HCO_3^-\) accepts a proton (\(H^+\)) from \(H_2O\) (since \(H_2O\) donates \(H^+\) to form \(OH^-\)), so it acts as a base.

Answer:

\(HCO_3^-(aq)+H_2O(l)
ightleftharpoons CO_3^{2 - }(aq)+H_3O^+(aq)\)