Question

He equation for the dissociation of pyridine is

C5H5N(aq) + H2O(l) ⇌ C 5H5NH+(aq) + OH-(aq) Kb = 1.9 × 10-9

Calculate the pH of a pyridine solution that has a concentration of 9.2 M. Round your answer to two decimal places.

Answer 1

10.10

Step-by-step explanation:

Step 1: Write the basic dissociation reaction for pyridine

C₅H₅N(aq) + H₂O(l) ⇌ C₅H₅NH⁺(aq) + OH⁻(aq) Kb = 1.9 × 10⁻⁹

Step 2: Calculate [OH⁻]

For a weak base, we will use the following expression.

[OH⁻] = √(Cb × Kb) = √(9.2 × 1.9 × 10⁻⁹) = 1.3 × 10⁻⁴ M

Step 3: Calculate pOH

We will use the definition of pOH.

pOH = -log [OH⁻] = -log 1.3 × 10⁻⁴ = 3.9

Step 4: Calculate pH

We will use the following expression.

pH = 14 - pOH = 14 - 3.9 = 10.10