What color change occurs when an acid is added to blue litmus paper?

What color change occurs when an acid is added to blue litmus paper?

• A. Blue litmus red
• B. Red litmus blue
• C. Litmus unchanged
• D. Litmus turns green

Answer: (A)

Litmus paper acts as a simple pH indicator. Blue litmus turns red in acidic solutions because the added acid lowers the pH enough to change the dye’s color. So when an acid is present, blue litmus paper changes to red. If the solution were neutral or basic, the blue paper would stay blue (and red litmus would turn blue in a base), but in this situation the acid causes the blue to become red.

Litmus paper acts as a simple pH indicator. Blue litmus turns red in acidic solutions because the added acid lowers the pH enough to change the dye’s color. So when an acid is present, blue litmus paper changes to red. If the solution were neutral or basic, the blue paper would stay blue (and red litmus would turn blue in a base), but in this situation the acid causes the blue to become red.