explain why pure dry benzoic acid do not
affect litmus paper
Litmus paper measures the acidity of a liquid (aqueous) solution.
Pure dry benzoic acid does not affect litmus paper because it is a weak acid. Litmus paper is commonly used to test for the presence of acids or bases in a solution. It changes color in the presence of an acidic or basic solution.
Benzoic acid is a weak acid, meaning it only partially dissociates in water to release hydrogen ions (H+). Litmus paper is sensitive to strong acids that readily produce a higher concentration of hydrogen ions. Weak acids like benzoic acid do not have a strong enough concentration of hydrogen ions to cause a color change in litmus paper.
To determine if benzoic acid is acidic, a different method such as pH measurement with a pH meter or indicator solutions specifically designed for weak acids would be more appropriate. These methods can detect the slightly acidic nature of benzoic acid even though it does not show a visible response with litmus paper.