What is the formula for calculating the pH of a solution?

The pH of a solution is calculated using the formula pH = -log[H⁺], which means it measures the negative logarithm of the hydrogen ion concentration in a solution. As the concentration of hydrogen ions increases, the pH value decreases, indicating a more acidic solution. Conversely, a lower concentration of hydrogen ions results in a higher pH, reflecting a more basic or alkaline solution.

This calculation is fundamental in chemistry for understanding the acidity or basicity of a given solution. The logarithmic nature of the equation means that each whole number change in pH represents a tenfold change in hydrogen ion concentration, which is critical when analyzing reactions in aqueous solutions.

In the context of the other options, while one of them suggests using the hydroxide ion concentration and another includes a logarithmic expression, they do not correctly reflect the relationship between pH and the hydrogen ion concentration. This distinction is essential for accurately determining the pH of any acidic or basic solution.