What is the name of the chemically treated paper used to test the acidity or alkalinity of a product?

The correct answer is litmus paper because it is specifically designed to assess the pH level of a solution, indicating whether it is acidic or alkaline. Litmus paper comes in two colors: red and blue. Red litmus paper turns blue in the presence of a base, while blue litmus paper turns red in acidic conditions. This color change provides a simple and immediate way to identify the acidity or alkalinity of a product without the need for complex measurements or equipment.

While pH paper can also serve this purpose, it is often associated with a broader range of pH testing, providing a more precise numerical value for pH levels rather than the simple categorical assessment that litmus paper offers. Indicator paper generally refers to a type of pH paper but can include a variety of indicators beyond just litmus, while test paper is a more generic term that does not specifically denote acidity or alkalinity measurement. Thus, litmus paper is the most widely recognized term for the chemically treated paper used primarily for this specific purpose.