The pH of 0.800 M aqueous benzenesulfonic acid is 0.51 .What is the value of K_a for benzenesulfonic acid?

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Quizplus · Accepted Answer

The pH of the solution is given as 0.51, which means the hydrogen ion concentration [H+] is 10^(-0.51). To find the Ka (acid dissociation constant) for benzenesulfonic acid, we use the formula Ka = [H+][A-]/[HA], where [HA] is the concentration of the acid and [A-] is the concentration of the conjugate base. Since the acid is strong, we can assume it dissociates completely, so [H+] = [A-] = 10^(-0.51). The concentration of the undissociated acid [HA] is negligible in comparison. Therefore, Ka ≈ [H+]^2 / [HA] = (10^(-0.51))^2 / 0.800 = 0.19.

The PH of 0