Confused! TBR Error?

[TheBoneDoctah]

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Here is the question in TBR:

Which of the following would be the BEST choice to neutralize 25mL of 0.10 M HClO3?

a. 25mL 0.10M NaOH
b. 250mL 0.010M NH3
c. 25mL 0.10M HCl
d. 250mL 0.010M HCO2H

I know that the answer is NOT c or d because since HClO3 is an acid, we need a base here to neutralize. My confusion comes down to the fact that from what I have learned, HClO3 and HClO4 are both STRONG ACIDS. Therefore, I chose answer choice A which is correct. However, in the answer explanations, BR says:

HClO3 is a WEAK acid that can be neutralized using a base of some sort. Choice is a weak base, so it can not fully react.

Is this a mistake or is HClO3 weak?

 

[brood910]

Some chemists include HCIO3 (Chloric acid) as a strong acid though it is not universally recognized as one. But HCIO4 is surely a strong acid.

So, yes. It's a terrible question.

 

[BerkReviewTeach]

The AAMC materials are full of questions with "BEST" in all caps. If you've been through the AAMC materials or taken a real MCAT, I'm sure you are familiar with questions asking for the best answer. There will be plenty of questions where two answers will be correct statements, so you need to master the art of choosing the best answer. This is a "BEST" answer question, so it's beneficial to understand how to approach them.

It's a moot point for this question, but the pKa for that acid is -0.2. This means that it dissociates about 60%, which is close enough to "fully dissociated" that it falls on the fence between strong and weak. In the typical definition, fully dissociated is 99% or greater, so it's a weak acid by that definition. However, given that the question is asking for the best answer, it's wasted energy to debate yourself over it. The best base to add to an acid is the strongest one, as it will ensure complete reaction. Whether the acid in the question is strong or weak, the best choice for the base is the strongest one, NaOH. This is actually a very good question in that it tests information and emphasizes a test nuance.