What color does methyl orange indicate in an acidic solution?

• A. Yellow
• B. Red
• C. Purple
• D. Clear

Answer: (B)

When a pH indicator is used, its color depends on how many hydrogen ions are present. Methyl orange changes from red in acidic solutions to yellow in basic ones, passing through orange as the pH crosses its transition range. In acidic conditions, the indicator is in its protonated form, which absorbs blue-green light and reflects red. So the color you see in an acidic solution is red. Yellow would indicate a basic environment, purple isn’t produced by methyl orange in its visible range, and clear isn’t observed within its normal indicator behavior.