Step 1: H2SeO3(aq) <-> HSeO3-(aq) + H+(aq) Ka1 = 2.1 x 10^-3 Step 2: HSeO3-(aq) <-> SeO3^2-(aq) + H+ — Acids and Bases Chemistry Question
Question
Step 1: H2SeO3(aq) <-> HSeO3-(aq) + H+(aq) Ka1 = 2.1 x 10^-3
Step 2: HSeO3-(aq) <-> SeO3^2-(aq) + H+(aq) Ka2 = 5.3 x 10^-9
The step-wise dissociation of selenous acid, H2SeO3(aq), is represented by the equations above. Which of the following best helps explain why the value of Ka2 is so much smaller than the value of Ka1?
The Se atom in H2SeO3(aq) is in a higher oxidation state than the Se atom in HSeO3-(aq).
Water is more attracted to HSeO3-(aq) ions than to SeO3^2- ions, which drives the step 2 equilibrium toward the reactant.
The HSeO3-(aq) ions produced in step 1 are asymmetrical, but the SeO3^2- ions produced in step 2 are symmetrical.
Removing the first H+ from H2SeO3(aq) requires less energy than removing the second H+, because the second H+ is removed from a negatively charged species.