The following plot shows two pH titration curves, each representing the titration of 50.0 mL of 0.100 M acid with 0.100 M NaOH:

. (a) Which of the two curves represents the titration of a strong acid? Which represents a weak acid?

Verified step by step guidance

1. Identify the initial pH of each curve. The curve with the lower initial pH represents the strong acid, while the curve with the higher initial pH represents the weak acid.
2. Observe the shape of the titration curves. The strong acid will have a more pronounced and steeper vertical section at the equivalence point compared to the weak acid.
3. Determine the pH at the equivalence point. For a strong acid titration, the pH at the equivalence point will be around 7, while for a weak acid, it will be above 7.
4. Compare the buffering regions before the equivalence point. The weak acid will show a more significant buffering region, indicated by a more gradual slope before the steep rise.
5. Conclude which curve represents the strong acid and which represents the weak acid based on the initial pH, shape of the curve, pH at the equivalence point, and buffering regions.

Key Concepts

Titration Curves

Titration curves graphically represent the change in pH of a solution as a titrant is added. The shape of the curve indicates the strength of the acid or base being titrated. A steep rise in pH indicates a strong acid or base, while a more gradual slope suggests a weak acid or base. The equivalence point, where the amount of titrant equals the amount of substance being titrated, is crucial for determining the strength of the acid or base.

Strong vs. Weak Acids

Strong acids, such as hydrochloric acid (HCl), completely dissociate in water, resulting in a sharp increase in pH during titration. In contrast, weak acids, like acetic acid (CH₃COOH), only partially dissociate, leading to a more gradual pH change. This difference in dissociation behavior is reflected in the titration curves, where strong acids show a steep slope at the equivalence point, while weak acids exhibit a more gradual slope.

pH and Neutralization

pH is a measure of the acidity or basicity of a solution, with lower values indicating acidic conditions and higher values indicating basic conditions. During a titration, the goal is to reach a neutralization point, where the acid and base completely react. The pH at this point can vary depending on whether a strong or weak acid is involved, influencing the shape of the titration curve and the final pH after the addition of the titrant.