Chemistry Practice Problems Ka and Kb Practice Problems Solution: Acidity of the hypohalous oxyacids (YOH) as a func...

Solution: Acidity of the hypohalous oxyacids (YOH) as a function of electronegativity of Y.At equilibrium, which of the two species with a halogen atom (green) is present in greater concentration?

Problem


Space-filling models show the reaction of halogen-OH acids with water.  A table lists dissociation constants. The overall reaction is Y-OH plus H2O goes, via a two-headed arrow, to YO- plus H3O+.  The reaction proceeds in the following steps: 1. YOH: As the electronegativity of Y increases, electron density shifts toward Y. 2. YOH: The O-H bond becomes more polar. 3. H3O+: Protons are more readily transferred to H2O, leading to increased acid strength.
Acidity of the hypohalous oxyacids (YOH) as a function of electronegativity of Y.

At equilibrium, which of the two species with a halogen atom (green) is present in greater concentration?

Solution

Establish how Ka is related to the concentration of H3O+ and determine which among the hypohalous acids will be most acidic

Recall that Ka represents the dissociation of H3O+ when the weak acid reacts with water.

As an example, weak acid HA will react with water to form H3Oion:

HA (aq) + H2O (l) ⇋ A(aq) + H3O+ (aq)

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