a) Given pOH = 8.03, we can find the pH, [OH-], and [H3O+] using the following relationships:
pH + pOH = 14 (at 25°C)
1. pH = 14 - pOH
pH = 14 - 8.03
pH = 5.97
2. [OH-] = 10^(-pOH)
[OH-] = 10^(-8.03)
[OH-] ≈ 7.01 x 10^(-9) M
3. [H3O+] = 10^(-pH)
[H3O+] = 10^(-5.97)
[H3O+] ≈ 1.03 x 10^(-6) M
b) Given [H3O+] = 4.36 x 10^(-2) M, we can find the pH, pOH, and [OH-] using the following relationships:
1. pH = -log([H3O+])
pH = -log(4.36 x 10^(-2))
pH ≈ 1.36
2. pOH = 14 - pH
pOH = 14 - 1.36
pOH ≈ 12.64
3. [OH-] = 10^(-pOH)
[OH-] = 10^(-12.64)
[OH-] ≈ 3.98 x 10^(-13) M
So for the second case:
pH ≈ 1.36
pOH ≈ 12.64
[OH-] ≈ 3.98 x 10^(-13) M
Hope this helps you.
willkiddhill