What does blue litmus paper turning red indicate?

The transformation of blue litmus paper to red is a clear indication of the presence of an acidic solution. Litmus paper is a common pH indicator used in chemistry to test the acidity or alkalinity of a solution. In its natural state, litmus paper is blue. When it comes into contact with an acid, the paper changes color to red due to the reaction between the acid and the chemical compounds within the litmus dye.

This color change happens because acids release hydrogen ions (H⁺) in solution, which interact with the dye used in the litmus paper, thus altering its color. This phenomenon provides a simple yet effective means to determine whether a solution is acidic.

On the other hand, blue litmus paper remaining blue indicates that the solution is either neutral or basic. A basic solution would typically change red litmus paper to blue, confirming its alkalinity. Concentration of a solution refers to the amount of solute present in a solvent and does not directly affect the color change of litmus indicators. Therefore, the other options do not accurately describe the chemical reaction that occurs when blue litmus paper comes into contact with an acidic solution.