Summary
Highlights
pH indicators are substances that change color based on the pH of the solution, offering a qualitative way to measure pH without a pH meter.
Universal indicator is a mixture of various indicators capable of measuring pH across the entire scale (0-14). It displays a rainbow of colors: deep red for strong acids (pH 1-2), green for neutral solutions (pH 7), and dark blue or purple for strong alkaline solutions.
Litmus is an indicator commonly used as litmus paper. Blue litmus paper turns red in acidic conditions (pH < 7), while red litmus paper turns blue in alkaline conditions (pH > 7).
Phenolphthalein is used to determine the endpoint in titrations involving strong acids/strong alkalis or weak acids/strong alkalis. It changes from colorless to fuchsia pink at a pH of 8.2.
Methyl orange is used for strong acid/strong alkali or strong acid/weak alkali titrations. It is red at a pH below 3.1 and yellow at a pH above 4.4.
Indicators are substances that change color at a specific pH, known as their endpoint. Common indicators include universal indicator, litmus, phenolphthalein, and methyl orange.