How do you calculate the pH of a strong acid?

To calculate the pH of a strong acid, you use the formula pH = -log [H3O+]. Strong acids fully dissociate in solution, meaning that the concentration of hydronium ions (H3O+) in the solution is equal to the initial concentration of the acid. This relationship allows us to accurately determine the pH of the solution based on the concentration of H3O+ ions.

Using the logarithmic function, the pH value provides a scale of acidity where lower pH values indicate higher acidity. Therefore, by measuring the concentration of H3O+ ions and applying the logarithmic function, you can derive the corresponding pH value accurately.

In the context of the other options, other formulas relate to pH incorrectly. For instance, using the concentration of hydroxide ions (OH-) or incorrectly applying logarithmic principles would not yield the correct pH values for strong acids. This specific relationship between pH and hydronium ion concentration is essential for understanding the acidic nature of solutions in aqueous chemistry.