To calculate the pH of a 0.1 M solution of hydrochloric acid HCl , we need to know the concentration of hydrogen ions H+ in the solution. HCl is a strong acid, which means it completely dissociates in water:HCl H+ + Cl-Since HCl completely dissociates, the concentration of H+ ions in the solution will be equal to the concentration of HCl, which is 0.1 M.The pH of a solution is calculated using the formula:pH = -log10[H+]In this case:pH = -log10 0.1 pH = - -1 pH = 1So, the pH of a 0.1 M solution of hydrochloric acid is 1.