How is pH calculated from hydrogen ion concentration [H⁺]?

The pH of a solution is calculated using the formula pH = -log([H⁺]), which establishes a relationship between the hydrogen ion concentration and the pH scale. The negative logarithm is used because the pH scale is a logarithmic scale, allowing it to express very small concentrations of hydrogen ions in a manageable numerical format.

As the concentration of hydrogen ions increases, the pH value decreases, indicating a more acidic solution. Conversely, as the hydrogen ion concentration decreases, the pH value increases, suggesting a more basic or alkaline solution. The logarithmic nature means that each whole number change in pH represents a tenfold change in hydrogen ion concentration.

This formula effectively transforms the concentration of hydrogen ions, which can range from very dilute to concentrated levels, into a scale from 0 to 14, where lower values indicate higher acidity and higher values indicate basicity. Since pH is widely used to indicate the acidity or basicity of a solution, understanding this calculation is essential in chemistry and various applications in science and engineering.