What is the equation used to calculate pH?

The correct equation used to calculate pH is based on the concentration of hydrogen ions (H+) in a solution, and it is defined as the negative logarithm of the hydrogen ion concentration. When we write pH = -log[H+], we are essentially measuring how acidic or basic a solution is based on the concentration of hydrogen ions.

This relationship is critical in biochemistry and many biological processes, as pH affects enzyme activity, metabolic pathways, and the behavior of biomolecules. A lower pH corresponds to a higher concentration of hydrogen ions, indicating an acidic environment, while a higher pH indicates a basic environment with fewer hydrogen ions.

The other options do not correctly reflect how pH is calculated. The first option lacks the essential negative sign, meaning it does not accurately represent the logarithmic relationship with hydrogen ion concentration. The third option suggests a linear relationship, which does not align with the logarithmic scale of pH. The fourth option incorrectly emphasizes a logarithm of the negative hydrogen concentration, which is not relevant since concentrations cannot be negative. Thus, the correct definition that establishes the foundational understanding of pH in biochemical contexts is captured in the negative logarithmic equation.