Which will cause the greatest change in the pH of a buffer solution ? Select the correct answer below: the addition of a quantity of an acid that is equal to half of the solution’s buffer capacity the addition of a quantity of an acid that is equal to three fourths of the solution’s buffer capacity the addition of a quantity of an acid that is equal to the solution’s buffer capacity the addition of a quantity of an acid that is equal to one and a half times the solution’s buffer capacity
The Correct Answer and Explanation is:
Correct Answer: The addition of a quantity of an acid that is equal to one and a half times the solution’s buffer capacity
Explanation:
A buffer solution works by neutralizing small amounts of added acid or base, thereby resisting changes in pH. This buffering action relies on the presence of a weak acid and its conjugate base (or a weak base and its conjugate acid) in equilibrium. The key factor in a buffer’s ability to resist pH changes is its buffer capacity, which refers to the maximum amount of acid or base that can be added before the buffer is overwhelmed.
When acid is added to a buffer, it reacts with the conjugate base present in the solution. As long as the amount of acid added is within the buffer capacity, the pH change remains small. However, if the amount of acid exceeds the buffer capacity, the buffer components are no longer able to neutralize the added acid, and the pH changes rapidly.
In this question, four options describe different proportions of acid relative to the buffer capacity:
- Half of the buffer capacity: The buffer is still far from being overwhelmed. Only a small pH change will occur.
- Three fourths of the buffer capacity: The buffer is still functioning, although its components are more depleted. The pH will change more, but still modestly.
- Equal to the buffer capacity: The buffer is just at its limit. The pH change becomes significant.
- One and a half times the buffer capacity: This surpasses what the buffer can handle. There are not enough buffer components to neutralize all the added acid. As a result, the excess acid remains in solution, and the pH drops sharply.
Therefore, adding one and a half times the buffer capacity causes the greatest pH change because the buffer is overwhelmed and can no longer maintain pH stability.
