Which substance is commonly used as an acid-base indicator, which turns red in acidic solutions and blue in basic solutions?

The correct answer is Litmus paper.

Key Points

• Litmus paper is a common acid-base indicator used in laboratories.
• It turns red in acidic solutions (pH less than 7).
• It turns blue in basic solutions (pH greater than 7).
• Litmus paper is derived from lichens, which are symbiotic associations between fungi and algae.

Additional Information

• Acid-Base Indicators
  • Substances that change color based on the pH level of the solution they are in.
  • Common indicators include methyl orange, phenolphthalein, and bromothymol blue.
  • Each indicator has a specific pH range over which it changes color.
• pH Scale
  • A scale ranging from 0 to 14 used to measure how acidic or basic a solution is.
  • A pH of 7 is neutral, below 7 is acidic, and above 7 is basic.
• Lichens
  • Organisms formed from a symbiotic relationship between fungi and algae.
  • They are capable of surviving in harsh environments and are used to produce litmus.
• Uses of Litmus Paper
  • Commonly used in educational laboratories to teach about acids and bases.
  • Used for testing the acidity or alkalinity of various substances in industrial applications.