Which of the following 0.10 M aqueous solutions gives the lowest pH?

Question

BlackTom AI · Accepted Answer

Consider the general idea that for a given concentration, stronger acids yield lower pH due to larger dissociation.
Option 1: 'Since all are 0.10 M solutions of acids, the pH is the same for all solutions.' This is incorrect because acids differ in strength; a 0.10 M solution of a stronger acid will have a lower pH than a weaker one.
Option 2: 'HIO3(aq), pKa = 0.80' This has the smallest pKa among the listed acids, which means it is the strongest acid in this set and will produce the greatest hydrogen ion concentration at 0.10 M, leading to the lowest pH.
Option 3: 'HClO2(aq), pKa = 1.96' A higher pKa indicates a weaker acid than HIO3, so its dissociation is less complete and its pH will be higher than that of HIO3 at the same concentration.
Option 4: 'HIO(aq), pKa = 10.70' An extremely weak acid with a very large pKa will hardly dissociate, contributing almost no H+ and thus giving a relatively high pH compared with the others.
Option 5: 'HBrO(aq), pKa = 8.70' This is also a very weak acid (large pKa), so its solution will have a higher pH than the stronger acids listed, particularly compared to the 0.80 pKa species.
In summary, the pH of a 0.10 M solution correlates inversely with acid strength (lower pKa means stronger acid and lower pH). Therefore, the solution with the lowest pH is the one containing the strongest acid, namely HIO3 with pKa 0.80.

Which of the following 0.10 M aqueous solutions gives the lowest pH?

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