Acetic acid is known to be a weak acid. What will happen to the acidity of the solution when sodium acetate is added to acetic acid?
A. The solution will become more acidic.
B. The pH will remain the same.
C. The solution will become less acidic.
D. The solution will become less basic.
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The correct answer is C. The solution will become less acidic. :)
To determine what will happen to the acidity of the solution when sodium acetate is added to acetic acid, we need to understand the concept of acid-base equilibrium and the behavior of weak acids and their conjugate bases.
Acetic acid (CH3COOH) is a weak acid, meaning it only partially dissociates into ions in water. When acetic acid dissolves in water, it forms hydrogen ions (H+) and acetate ions (CH3COO-).
Sodium acetate (CH3COONa) is the conjugate base of acetic acid. It dissociates completely in water to form sodium ions (Na+) and acetate ions (CH3COO-).
When sodium acetate is added to acetic acid, the acetate ions (CH3COO-) produced by the dissociation of sodium acetate can react with the hydrogen ions (H+) from the acetic acid to form more nonionized acetic acid molecules (CH3COOH). This reaction is called the acetate ion acting as a base and the acetic acid acting as an acid.
The reaction can be represented as:
CH3COO- + H+ ⇌ CH3COOH
Since the acetate ions (CH3COO-) consume the hydrogen ions (H+) in the solution, the concentration of hydrogen ions decreases. As a result, the solution becomes less acidic, and the acidity decreases.
Therefore, the correct answer is:
C. The solution will become less acidic.
Write the ionization expression for HAc.
HAc ==> H^+ + AC^-
now K = (H^+)(Ac^-)/(HAc)
Now if NaAc is added, that increases the Ac^- (the common ion effect), that shifts the equilibrium to the left. What happens to the H^+ and how does that affect the pH. By the way, this is how you make a buffer solution.