Question

which of the following describes a solution that contains a buffer?

a. sodium hydroxide, a base, is added to the solution, and the ph of
the solution becomes higher.

b. formic acid is added to the solution, and the ph of the solution
becomes higher.

c. citric acid is added to the solution, and the ph of the solution
becomes lower.

d. acetic acid is added to the solution, but the ph of the solution
does not change.

Explanation:

A buffer solution resists changes in pH when small amounts of acid or base are added. Let's analyze each option:

• Option A: Adding a base (NaOH) increasing pH means the solution didn't resist pH change, so not a buffer.
• Option B: Adding formic acid (an acid) increasing pH is unusual and doesn't show buffering (acids usually lower pH), so not a buffer.
• Option C: Adding citric acid (an acid) lowering pH means the solution didn't resist pH change, so not a buffer.
• Option D: Adding acetic acid (an acid) and pH not changing shows the solution resisted pH change, which is the property of a buffer.

Answer:

D. Acetic acid is added to the solution, but the pH of the solution does not change.