To calculate the pH of a solution, you need to know the concentration of hydrogen ions (H+) in the solution. HCl is a strong acid that dissociates completely in water, so we can assume that all of the HCl molecules will dissociate into H+ ions and Cl- ions.
The number of moles of H+ ions in the solution will be equal to the number of moles of HCl that were added to the solution. In this case, we have 2.0 moles of HCl in 8.5 L of solution. To find the concentration of H+ ions, we need to divide the number of moles by the volume of the solution:
2.0 moles / 8.5 L = 0.2353 moles/L
Now that we know the concentration of H+ ions, we can calculate the pH of the solution using the following formula:
pH = -log[H+]
where [H+] is the concentration of hydrogen ions in moles/L. Substituting the value we calculated above, we get:
pH = -log(0.2353) = 0.628
Therefore, the pH of the solution is approximately 0.63.