To calculate the pH of a 0.1 M solution of hydrochloric acid HCl , we can use the formula:pH = -log10[H+]Since HCl completely ionizes in water, the concentration of hydrogen ions [H+] will be equal to the concentration of the HCl solution, which is 0.1 M.pH = -log10 0.1 pH = - -1 pH = 1The pH of a 0.1 M solution of hydrochloric acid is 1.