Final answer:
The pH of a 0.200 M HCl solution at 25 0C is 0.698.
Step-by-step explanation:
To calculate the pH of a solution, we need to know the concentration of the hydrogen ions (H+). In the case of a 0.200 M HCl solution, all of the HCl molecules ionize in water to form H+ ions and Cl- ions. Since HCl is a strong acid and ionizes completely, the concentration of H+ ions will be equal to the concentration of the HCl solution, which is 0.200 M.
The pH is calculated using the equation pH = -log[H+]. Substituting the concentration of H+ ions into the equation, we get pH = -log(0.200) = 0.698.