GED Science TestPhysical ScienceMedium
A student is observing an unknown solution. When they add a few drops of universal indicator, the solution turns a vibrant purple color. Based on this observation, what can the student conclude about the solution?
- AThe solution is strongly acidic.
- BThe solution contains a high concentration of salt.
- CThe solution is strongly basic.
- DThe solution is neutral.
Show answer & explanationAnswer & explanation
Correct answer: C. The solution is strongly basic.
Universal indicator changes color across the pH scale. A vibrant purple color typically indicates a strongly basic (alkaline) solution, corresponding to a high pH value (around 10-14).
Why the other options are wrong
- A. Strongly acidic solutions (pH 1-3) would turn universal indicator red or orange.
- B. The color of universal indicator is specific to pH, not directly to salt concentration, although some salts can affect pH.
- D. A neutral solution (pH 7) would turn universal indicator green.
Universal Indicator
A pH indicator made of a solution of several compounds that exhibits several color changes over a wide range of pH values to indicate the acidity or alkalinity of solutions.
- Changes color based on pH (potential of hydrogen).
- Red/Orange = Acidic (low pH)
- Green = Neutral (pH 7)
- Blue/Purple = Basic (high pH)
Memory trick: Remember 'Red for Acid, Green for Clean (Neutral), Blue for Base' with Universal Indicator.