What color does litmus paper turn in an acidic solution?

Litmus paper is a common pH indicator used to determine whether a solution is acidic or basic. When litmus paper is placed in an acidic solution, it undergoes a chemical change that causes it to turn red. This is a characteristic response of the litmus indicator, whose color changes are linked to the pH level of the solution.

In acidic environments, where the concentration of hydrogen ions is higher (pH less than 7), the red color is observed. This red color indicates that the solution has an excess of protons, which is a defining property of acids. Conversely, in basic (alkaline) solutions, the litmus paper would turn blue.

The other colors associated with litmus paper do not accurately represent the response in acidic solutions, as they are indicative of neutral or basic conditions rather than acidity. Thus, the correct response when litmus paper is placed in an acidic solution is red, confirming the presence of an acid.