Sciencemadness Discussion Board

Acid

Scapegrace - 17-4-2012 at 06:44

What exaactly does acid do does it break things down into there elemental form? or does it oxidize them.

[Edited on 17-4-2012 by Scapegrace]

stygian - 17-4-2012 at 06:52

Acids typically protonate substance, given it is strong enough. :)

Vikascoder - 17-4-2012 at 06:53

there are various typesf acid each has its different nature. if you talk particularly about nitric acid it oxides the things.

Nicodem - 17-4-2012 at 08:43

There are at least three historical definitions of what an acid (and consequently also what a base) is. See http://en.wikipedia.org/wiki/Acid

The Lewis' definition is what is today commonly used: "A Lewis acid is a species that accepts a pair of electrons from another species; in other words, it is an electron pair acceptor." (wikipedia)
By this definition the "acids typically protonate substance" does not encompass them all.
Beware, that the definition talks about electron pairs. Do not mix up with oxidants which accept unpaired electrons!

The essential property of an acid is its equilibrium constant for its reactions with bases. These constants are commonly expressed as the negative logarithm of the constant, as pKa's. The pKa values are measured and tabulated. If the base is not defined, the pKa value usually refers to dissociation in a solvent that acts as the base (for example, in aqueous solution). For example, the aqueous pKa of acetic acid is 4.76, while the aqueous pKa of H<sub>3</sub>O<sup>+</sup> (protonated water) is -1.7. From the base perspective, this means that water in water is a 10^6.46 times weaker base than the acetate ion in water. The consequence of this is that acetic acid is mainly undissociated in water, because water is not a strong enough base to efficiently deprotonate it. With HBr (pKa is -9) the case is the opposite (water is a strong enough base to nearly quantitatively deprotonate HBr). Water is not only a very weak base. The aqueous pKa of water (H<sub>2</sub>O) is only 15.7. Water is thus also a very weak acid. Substances that can act as acids and bases at the same time (many substances are such) are called amphoteric substances.
Quote: Originally posted by Vikascoder  
there are various typesf acid each has its different nature. if you talk particularly about nitric acid it oxides the things.

The redox abilities of an acid has nothing to do with it being an acid!

DerAlte - 17-4-2012 at 10:33

@ Nicoderm: I am sure you lost their attention in your first line. Neat summary, though, even if it fell on deaf ears!
Der Alte

Bombaholic - 17-4-2012 at 17:15

Since were on the subject of acids do you need nitric acid to nitrate things (sounds like a noob question) because I was looking at the process of making ETN and its just sulfuric acid >%95 ammonium nitrate and erythritol can you just use the acid and ammonium nitrate to nitrate other sugars or anything else cause if so why go through the trouble of trying to get nitric acid?

Bot0nist - 17-4-2012 at 17:21

Quote: Originally posted by Bombaholic  
Since were on the subject of acids do you need nitric acid to nitrate things (sounds like a noob question) because I was looking at the process of making ETN and its just sulfuric acid >%95 ammonium nitrate and erythritol can you just use the acid and ammonium nitrate to nitrate other sugars or anything else cause if so why go through the trouble of trying to get nitric acid?

http://www.sciencemadness.org/talk/viewthread.php?tid=19212&...

Déjà vu...

PS. See the forum's posting guidelines before getting started.

[Edited on 18-4-2012 by Bot0nist]