Calculate the hydroxide ion concentration in an aqueous solution with a pH of 9.85 at 25°C. 8.7 × 10-10 M 1.4 × 10-10 M 4.2 × 10-10 M 6.5 × 10-5 M 7.1 × 10-5 M

7,1x10⁻⁵M = [OH⁻]

Explanation:

pH is the -log of hydronium ion. pOH is -log of hydroxide ion. Knowing pH + pOH = 14:

14 = 9,85 + pOH

pOH = 14 - 9,85

pOH = 4,15

-log [OH⁻] = 4,15

10^-4,15 = [OH⁻]

7,1x10⁻⁵M = [OH⁻]

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