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Topic: bond strength of acid?  (Read 1654 times)

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Offline antimatter101

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bond strength of acid?
« on: November 01, 2012, 07:04:47 AM »
 >:( >:( >:(

THis is COMMON SENSE to everyone in the world -  an acid is a substance that dissolves in water to form h+ and something- ions, the reason because the bond between oxygen and hydrogen in those cases are exceptionally weak.
I justified it by looking at the oxygen-hydrogen bond strength, and found it on one website to be 366 kj/mol and wikipedia 460kj/mol.
Take nitrous acid, for example, with the chemical formula HNO2. The nitrogen atom has a double bond to an oxygen atom, and a single bond to another oxygen which is bonded to the hydrogen.We know the bond strength of oxygen to hydrogen is 366/460 kj/mol, right? THen I revisited my workbook and found the strength of the hitrogen-oxygen single bond to be only 201 kj/mol - much weaker that the oxygen-hydrogen bond. What the &^%$!

Moreover compounds such as carbon dioxide and silicon dioxide (Both no hydrogens) are also acids. Chlorine and other halogens turn blue litmus paper red before bleaching it. This is very confusing!

Help please!

Offline Babcock_Hall

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Re: bond strength of acid?
« Reply #1 on: November 01, 2012, 09:16:18 AM »
I don't have time to do this topic full justice this morning.  However, one thing worth mentioning is that bond strengths refer to homolytic breaking of a bond, which create two radicals (each nucleus departs with one electron from the bond).  On the other hand, the dissociation of a proton, H+, from a substance is a heterolytic process, in which the proton does not stay with either of the two electrons.

Carbon dioxide can combine with water to make H2CO3, carbonic acid.  The conjugate base is the well-known bicarbonate anion, HCO3-.

Offline antimatter101

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Re: bond strength of acid?
« Reply #2 on: November 02, 2012, 04:50:59 AM »
Thanks for the answer!

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