NCEA Level 2 Organic Chemistry Practice Exam 2026 - Free Level 2 Chemistry Practice Questions and Study Guide

When an organic acid is added to a solution containing a pH indicator, the color of the indicator changes based on the strength of the acid. This occurs because different pH indicators have specific pH ranges in which they change color, and organic acids can influence the acidity of the solution.

Strong acids significantly lower the pH, often causing the indicator to switch to a more acidic color. In contrast, weaker acids may result in smaller changes in pH, leading to different color transitions depending on how weak or strong the acid is relative to the indicator’s transition range. Thus, the indicator effectively reflects the acidity of the solution, resulting in distinct color changes tied directly to the nature of the acid added. This is why the correct understanding of how pH indicators respond to different acids leads to the conclusion that the color change is indeed based on the strength of the acid.