In an acid–base titration, what is meant by the end point?

• A. The point at which an observable change (such as an indicator color change or instrument signal change) indicates the titration should be stopped
• B. The point at which stoichiometric amounts of titrant and analyte have reacted exactly (the equivalence point)
• C. The initial condition before any titrant is added, where the analyte concentration is at its maximum
• D. The point at which the solution becomes neutral at $pH=7$ regardless of the acids or bases involved

Answer: (A)

Verified step by step guidance

1. Understand that in an acid-base titration, the equivalence point is the theoretical point where stoichiometric amounts of acid and base have completely reacted. This is a precise chemical concept based on mole ratios.
2. Recognize that the end point is an experimentally observed event during the titration, often indicated by a visible change such as a color change of an indicator or a change in an instrument signal.
3. Note that the end point is used practically to decide when to stop adding titrant, and it ideally occurs very close to the equivalence point but is not necessarily exactly the same.
4. Be aware that the solution's pH at the end point depends on the nature of the acid and base involved and is not always neutral (pH = 7). Therefore, the end point is not defined by the solution becoming neutral.
5. Summarize that the end point is the point during titration where an observable change signals that the titration should be stopped, distinguishing it from the equivalence point, which is a theoretical stoichiometric concept.