What does pH measure?

pH is a scale used to quantify the acidity or basicity of an aqueous solution, which is specifically determined by the hydrogen ion concentration. The pH scale typically ranges from 0 to 14, where values below 7 indicate acidic solutions (higher hydrogen ion concentration), values above 7 indicate basic (or alkaline) solutions (lower hydrogen ion concentration), and a pH of 7 indicates a neutral solution.

Understanding that pH measures the hydrogen ion concentration is crucial in many fields, including chemistry and biology. It determines how chemical reactions occur, influences the solubility of various compounds, and impacts biological processes.

The other choices pertain to different measures and do not relate to pH. For instance, glucose concentration is a measure of sugar content in a solution, which is unrelated to hydrogen ions. Basicity, while related to pH, is more of a qualitative feature rather than a direct measure, and mass pertains to the amount of substance rather than its acidity or basicity. Thus, the key aspect of pH is its definition as a measure of hydrogen ion concentration.