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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: labratattack on February 05, 2019, 12:31:01 AM

Title: Why does acetic acid + NaOH have a larger ∆Hrxn than HCl + NaOH?
Post by: labratattack on February 05, 2019, 12:31:01 AM
referred here from reddit.

Why does acetic acid + NaOH have a larger ∆Hrxn than HCl + NaOH?

This question comes from general chemistry II lab and is not for a grade (not sure if that matters here or not), but more of a challenge question. Will someone help me understand? Thank you
Title: Re: Why does acetic acid + NaOH have a larger ∆Hrxn than HCl + NaOH?
Post by: mjc123 on February 05, 2019, 04:32:18 AM
What is the actual reaction that happens in HCl + NaOH?
What else happens in AcOH + NaOH?
Title: Re: Why does acetic acid + NaOH have a larger ∆Hrxn than HCl + NaOH?
Post by: labratattack on February 05, 2019, 12:44:09 PM
HCl and NaOH both completely dissociate and form water plus ions. Acetic acid is a weak acid and doesn’t completely dissociate but NaOH does. So, because acetic acid doesn’t completely dissociate it’s ΔHrxn is greater?

Is that on the right track?
Title: Re: Why does acetic acid + NaOH have a larger ∆Hrxn than HCl + NaOH?
Post by: mjc123 on February 06, 2019, 04:34:24 AM
Yes. Can you write equations for the reactions that occur? Assume (as I assume the question does) that you start with aqueous solutions of the reagents, so you don't have to consider the dissociation of e.g. NaOH - it's already dissociated.