When litmus paper is placed in an acidic solution, which color does it take?

When litmus paper is placed in an acidic solution, which color does it take?

• A. Red
• B. Blue
• C. Violet
• D. Yellow

Answer: (A)

Litmus paper acts as a simple pH indicator that changes color with hydrogen ion concentration. In an acidic solution, the litmus dye becomes protonated and shifts toward red, so the paper appears red. This is why red is observed when litmus is placed in acid. If blue litmus paper were used, it would also turn red in acid, while red litmus would stay red; colors like violet or yellow aren’t produced by litmus in acidic environments.

Litmus paper acts as a simple pH indicator that changes color with hydrogen ion concentration. In an acidic solution, the litmus dye becomes protonated and shifts toward red, so the paper appears red. This is why red is observed when litmus is placed in acid. If blue litmus paper were used, it would also turn red in acid, while red litmus would stay red; colors like violet or yellow aren’t produced by litmus in acidic environments.