Question

Find the pH of a mixture that is 0.150 M in HF (Ka = 3.5 x 10⁻⁴) and 0.100 M in HClO (Ka = 2.9 x 10⁻⁸)

Answer 1

The pH of a mixture that is 0.150 M in HF and 0.100 M in HClO is approximately 1.64, with the calculation based primarily on the contribution of HF as the stronger acid.

Step-by-step explanation:

To find the pH of a mixture that is 0.150 M in HF (Ka = 3.5 x 10⁻⁴) and 0.100 M in HClO (Ka = 2.9 x 10⁻⁸), one must consider that HF is a stronger acid than HClO since it has a larger acid dissociation constant (Ka). This means that HF will contribute more significantly to the concentration of H+ ions in the solution than HClO. Since HClO is a much weaker acid compared to HF, its contribution to the H+ can be neglected for this approximation. We can calculate the concentration of H+ from the dissociation of HF using the formula for the ionization of a weak acid: [H+] = √(Ka * [HA]), where [HA] is the concentration of the acid (HF in this case).

Inserting the given values, [H+] = √(3.5 x 10⁻⁴ * 0.150) ≈ 2.3 x 10⁻⁲ M. Then, the pH of the solution is calculated using the formula pH = -log([H+]). Therefore, pH ≈ -log(2.3 x 10⁻⁲) ≈ 1.64.