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1. HCl is a strong acid.

  1. What is the hydrogen ion concentration, [H+], of a 0.0025 M solution of HCl?
  2. What is the pH of a 0.0025 M solution of HCl?

1. NaOH is a strong base.

  1. What is the hydrogen ion concentration, [H+], of a 0.0025 M solution of NaOH?
  2. What is the pH of a 0.0025 M solution of NaOH?

1. A strong acid completely dissociates, therefore, the hydrogen ion concentration of a 0.0025 M solution of HCl is 0.0025 M

  1. [H+] = 0.0025 M = 2.5 x 10-3 M
  2. pH = -log([H+]) = -log(2.5 x 10-3) = 2.60

2. A strong base completely dissociates, therefore, the hydroxyl ion concentration of a 0.0025 M solution of NaOH is 0.0025 M

  1. [H+] = Kw/[OH-] = (1 x 10-14 M2)/(2.5 x 10-3 M) = 4.0 x 10-12 M.
  2. pH = -log([H+]) = -log(4.0 x 10-12) = 11.40