Answer
a. [OH-] = 6.7 $\times 10^{-6}$ M
b. [OH-] = 1.1 $\times 10^{-6}$ M
c. [OH-] = 4.5 $\times 10^{-6}$ M
d.[OH-] = 1.4 $\times 10^{-11}$ M
Work Step by Step
Kw=[$H_{3}O$+][OH-]
[OH-] = $\frac{Kw}{[H_{3}O+]}$
*** Kw= 1 $ \times 10^{-14}$
a.
[OH-] = $\frac{Kw}{[H_{3}O+]}$
[OH-] = $\frac{1 \times 10^{-14}}{1 \times 10^{-9}}$
[OH-] = 6.7 $\times 10^{-6}$ M
b.
[OH-] = $\frac{Kw}{[H_{3}O+]}$
[OH-] = $\frac{1 \times 10^{-14}}{9.3 \times 10^{-6}}$
[OH-] = 1.1 $\times 10^{-6}$ M
c.
[OH-] = $\frac{Kw}{[H_{3}O+]}$
[OH-] = $\frac{1 \times 10^{-14}}{2.2 \times 10^{-6}}$
[OH-] = 4.5 $\times 10^{-6}$ M
d.
[OH-] = $\frac{Kw}{[H_{3}O+]}$
[OH-] = $\frac{1 \times 10^{-14}}{7.4 \times 10^{-4}}$
[OH-] = 1.4 $\times 10^{-11}$ M