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Problem 3 - Entrance Test

What is the pH of a 10^-8 M solution of HCl?

Correct: C

Since the concentration of HCl is very low, we must consider the auto-ionization of water. [H+] = 10^-8 (from HCl) + 10^-7 (from water) = 1.1 x 10^-7 M. pH = -log[H+] = -log(1.1 x 10^-7) ≈ 6.96.