Which of the following is the strongest acid? a. pH = 12
b. pOH = 5
c.[H+] = 1 x 10-8
d. pOH = 12

d. pOH = 12 => pH = 14 - 10 = 2 => most acidic

Explanation:

pH = -log[H⁺] => [H⁺] = 10^-pH

By definition, if ...

[H⁺] > 10⁻⁷ > [OH⁻] => pH < -log(10⁻⁷) < 7 => pOH > 14 - 7 > 7 => acidic solution

[H⁺] = 10⁻⁷ = [OH⁻]  => pH = -log(10⁻⁷) = 7 => pOH = 14 - 7 = 7 => neutral solution

[H⁺] < 10⁻⁷ < [OH⁻]  => pH > -log(10⁻⁷) > 7 => pOH < 14 - 7 < 7 => basic solution

∴ From most basic to most acidic ...

a. pH = 12 => most basic

b. pOH = 5 => pH = 14 - 5 = 9

c. [H⁺] = 1 x 10⁻⁸ => pH = -log(10⁻⁸) = -(-8) = 8

d. pOH = 12 => pH = 14 - 10 = 2 => most acidic