MCAT Chemical and Physical Foundations of Biological Systems Practice Exam 2025 – Comprehensive All-in-One Guide for Exam Success!

The concentration of hydrogen ions, represented as [H+], is directly related to the pH of a solution through the equation [H+] = 10^(-pH). The pH scale is a logarithmic scale that measures the acidity or basicity of a solution, defined as the negative logarithm of the hydrogen ion concentration. Thus, to calculate the concentration of hydrogen ions from a given pH, you can use the relationship that 10 raised to the power of the negative pH will yield the hydrogen ion concentration.

For example, if a solution has a pH of 3, the hydrogen ion concentration would be [H+] = 10^(-3) mol/L, which equals 0.001 mol/L. This relationship illustrates that lower pH values correspond to higher concentrations of hydrogen ions, indicative of more acidic solutions, while higher pH values correspond to lower concentrations, indicating more basic solutions.

The other expressions do not accurately reflect this logarithmic relationship between pH and hydrogen ion concentration, reinforcing the significance of understanding how to manipulate logarithmic functions in chemistry.