What is the formula for calculating the pH of a strong acid?

The correct formula for calculating the pH of a strong acid is pH = -log[H^+]. This equation is derived from the definition of pH, which is a measure of the hydrogen ion concentration in a solution. For a strong acid, which completely dissociates in solution, the concentration of hydrogen ions [H^+] is equal to the concentration of the acid itself.

The logarithmic function in the formula reflects the fact that pH is a logarithmic scale; therefore, a change in hydrogen ion concentration by a factor of 10 results in a change in pH by 1 unit. Therefore, using this formula, if you know the concentration of hydrogen ions in the solution, you can directly compute the pH by taking the negative logarithm of that concentration.

This relationship underlines the principle that lower pH values indicate higher concentrations of hydrogen ions, which is characteristic of strong acids.