Question

Consider a buffer solution of carbonic acid and bicarbonate:

A) Write the general equation for the buffer solution reaction.
B) A strong acid, perchloric acid, is introduced into the solution. Include an explanation of the direction of the equilibrium shift (based on the general equation).
C) A strong base, lithium hydroxide, is introduced into the solution. Include an explanation of the direction of the equilibrium shift (based on the general equation).

Answer 1

A) A buffer solution of carbonic acid and bicarbonate resists pH changes. The general equation for the buffer solution reaction is H₂CO₃(aq) ⇌ HCO₃⁻(aq) + H⁺(aq). B) The addition of a strong acid shifts the equilibrium to the left, forming more carbonic acid. C) The addition of a strong base shifts it to the right, using up hydroxide ions and producing more hydronium ions.

Step-by-step explanation:

A) A buffer solution is a mixture of a weak acid and its conjugate base that can resist pH changes when small amounts of strong acid or base are added. In the case of the carbonic acid and bicarbonate buffer system, the general reaction can be written as:

H₂CO₃(aq) ⇌ HCO₃⁻(aq) + H⁺(aq)

B) When a strong acid like perchloric acid (HClO4) is added to the solution, it increases the concentration of H+ ions. As a result, the equilibrium will shift to the left according to Le Chatelier's principle to minimize the change in pH by using up some of the added H+ to form more carbonic acid.

C) Conversely, when a strong base like lithium hydroxide (LiOH) is added, it will react with H+ ions to form water. This decreases the concentration of H⁺ ions, causing the equilibrium to shift to the right to produce more hydronium ions (H⁺), thereby using up the OH- ions and limiting the increase in pH.