Answer:
1 x 10⁻¹¹ M
Explanation:
(Step 1)
Determine the pH.
pH = -log[H⁺]
pH = -log[1 x 10⁻³ M]
pH = 3
(Step 2)
Determine the pOH.
pH + pOH = 14
3 + pOH = 14
pOH = 11
(Step 3)
Determine the hydroxide (OH⁻) concentration.
[OH⁻] = 10^-pOH
[OH⁻] = 10⁻¹¹
[OH⁻] = 1 x 10⁻¹¹ M