What is the hydronium ion concentration of a 0.150 mol L^-1 hypochlorous acid solution with K_a = 3.5 × 10^-8?The equation for the dissociation of hypochlorous acid is below: A)1.9 × 10^-4mol L^-1 B)7.2 × 10^-4mol L^-1 C)2.8 × 10^-5mol L^-1 D)7.2 × 10^-5mol L^-1

Question

Quizplus · Accepted Answer

The equation for the dissociation of hypochlorous acid is:

HClO(aq) + H2O(l) ⇌ H3O+(aq) + ClO-(aq)

Where H3O+ is the hydronium ion concentration.

The Ka expression for this reaction is:

Ka = [H3O+][ClO-]/[HClO]

We are given the concentration of HClO as 0.150 mol/L and the Ka value as 3.5x10^-8.

Let x be the hydronium ion concentration at equilibrium.

Then, using the Ka expression:

3.5x10^-8 = x^2 / (0.150 - x)

Ignoring x in comparison to 0.150 gives the approximation:

3.5x10^-8 = x^2 / 0.150

Rearranging and solving for x:

x = 7.2x10^-5 M

Therefore, the hydronium ion concentration is 7.2x10^-5 mol/L or 7.2x10^-5 M.

The answer is D.

What Is the Hydronium Ion Concentration of a 0