Question

Which observation is useful for the chemist to determine when a basic solution becomes acidic?

A. The indicator
B. Measured amounts of a weak acid
C. A color change
D. A change in the chemical composition of the solution

Answer 1

To determine when a basic solution becomes acidic, a chemist uses an acid-base indicator like phenolphthalein, which changes color at a specific pH value, indicating the equivalence point in a titration.

Step-by-step explanation:

A chemist can determine when a basic solution becomes acidic by observing a color change using an acid-base indicator. An indicator undergoes a distinct color shift at a specific pH value. For example, phenolphthalein is an indicator that changes from colorless to pink as the solution transitions from acidic to basic, which is particularly useful during titrations to identify the equivalence point. The chemistry of indicators is based on acid-base equilibria, where the indicator changes from one color form to another based on the concentration of hydronium ions in solution.