Hz is a weak acid. an aqueous solution of hz is prepared by dissolving 0.020 mol of hz in sufficient water to yield 1.0 l of solution. the ph of the solution was 4.93 at 25.0oc. the ka of hz is a) 1.2×10−5b) 6.9×10−9c) 1.4×10−10d) 9.9×10−2e) 2.8×10−12

B) 6.9 × 10⁻⁹

Explanation:

HZ is a weak acid that ionizes according to the following generic equation.

HZ(aq) ⇄ H⁺(aq) + Z⁻(aq)

First, we have to calculate the concentration of H⁺ using the pH.

pH = -log [H⁺]

[H⁺] = antilog -pH = antilog -4.93 = 1.17 × 10⁻⁵

Then, we have to calculate the initial concentration of the acid (Ca).

Finally, we can calculate the acid dissociation constant (Ka) using the following expression.

i'm pretty sure its b i might be wrong though!