Question

Rank the following solutions from the highest [H3O+] (1) to the lowest [H3O+] (5).

[H3O+] = 3.16 × 10–4 M
[OH–] = 4.35 × 10–2 M
pH = 1.05
pOH = 7.0
pOH = 4.0

Answer 1

Assuming Kw = 1.00×10⁻¹⁴ (25 °C), the [H3O+] values are:

- pH = 1.05 → [H3O+] = 10⁻¹.⁰⁵ = 8.91×10⁻² M
- [H3O+] = 3.16×10⁻⁴ M (given)
- pOH = 7.0 → pH = 7.0 → [H3O+] = 10⁻⁷ = 1.00×10⁻⁷ M
- pOH = 4.0 → pH = 10.0 → [H3O+] = 10⁻¹⁰ = 1.00×10⁻¹⁰ M
- [OH⁻] = 4.35×10⁻² M → [H3O+] = Kw/[OH⁻] = 1.00×10⁻¹⁴ / 4.35×10⁻² = 2.30×10⁻¹³ M

Ranked from highest [H3O+] (1) to lowest (5):

1. pH = 1.05
2. [H3O+] = 3.16×10⁻⁴ M
3. pOH = 7.0
4. pOH = 4.0
5. [OH⁻] = 4.35×10⁻² M