To calculate the pH of a 0.2 M solution of hydrochloric acid HCl , we need to use the formula:pH = -log10[H+]Hydrochloric acid is a strong acid, which means it completely dissociates in water. Therefore, the concentration of hydrogen ions [H+] in the solution will be equal to the concentration of the HCl solution.[H+] = 0.2 MNow, we can plug this value into the pH formula:pH = -log10 0.2 pH 0.70The pH of a 0.2 M solution of hydrochloric acid is approximately 0.70.