Question

Calculate the concentration of H3O+ in a solution that contains 6.25 × 10-9 M OH- at 25°C. Identify the solution as acidic, basic, or neutral.

Answer 1

[OH⁻] = 1.60 × 10⁻⁶ M

Basic

Step-by-step explanation:

Step 1: Given data

Concentration of H₃O⁺: 6.25 × 10⁻⁹ M

Step 2: Calculate the concentration of OH⁻

We will use the following expression.

Kw = [H₃O⁺] × [OH⁻] = 1.00 × 10⁻¹⁴

[OH⁻] = 1.00 × 10⁻¹⁴ / 6.25 × 10⁻⁹ = 1.60 × 10⁻⁶ M

Step 3: Calculate the pH

We will use the following expresion.

pH = -log [H₃O⁺] = -log (6.25 × 10⁻⁹) = 8.20

Since the pH > 7, the solution is basic.