Which color indicates a weak acid on universal indicator?

• A. Red
• B. Orange
• C. Green
• D. Purple

Answer: (B)

Universal indicator shows pH with a rainbow of colors, from red for very acidic solutions to purple for very basic ones, with green near neutral. A weak acid still has pH below 7, but not as low as a strong acid, so its color sits in the acidic part of the scale rather than the deepest red. That place on the scale is orange, indicating mild to moderate acidity. If it were a strong acid, the color would shift toward red; neutral solutions sit green; strong bases push toward purple. So the orange color best matches a weak acid on universal indicator.