Sciencemadness Discussion Board

Ph tester for solids

sirsomething - 10-2-2016 at 07:26

Hello everyone,


First of all thank you for your help.

I'd like to know if there are any ph testers for solids not diluted, where can I buy them and how much would they cost.

Thanks

JJay - 10-2-2016 at 07:29

A solid which is not diluted does not have a pH. There is a thread on understanding Bronsted-Lowry acid-base theory that you should read. You can find it using the search engine.

Detonationology - 10-2-2016 at 07:40

pH is calculated and measured by the quantity of H+ ions in solution. To my knowledge, ions will not dissociate when solid, but don't quote me.

Hmmm. Now I'm curious what were to happen to the ions in anhydrous sulfuric acid if were to somehow become frozen? They wouldn't be able to freely dissociate, right?

phlogiston - 10-2-2016 at 08:06

It will definately help if you could explain what you are trying to accomplish.

DraconicAcid - 10-2-2016 at 08:09

pH is only meaningful in dilute aqueous solution.

blogfast25 - 10-2-2016 at 08:16

Quote: Originally posted by JJay  
A solid which is not diluted does not have a pH. There is a thread on understanding Bronsted-Lowry acid-base theory that you should read. You can find it using the search engine.


Here it is:

http://www.sciencemadness.org/talk/viewthread.php?tid=65082
Quote: Originally posted by Detonationology  
pH is calculated and measured by the quantity of H+ ions in solution. To my knowledge, ions will not dissociate when solid, but don't quote me.

Hmmm. Now I'm curious what were to happen to the ions in anhydrous sulfuric acid if were to somehow become frozen? They wouldn't be able to freely dissociate, right?


The first point is really incorrect or at least very old fashioned: aqueous solution contain no free protons (H<sup>+</sup>;), only oxonium ions: H3O<sup>+</sup> (also some H5O2<sup>+</sup> and higher).

Your second point: H2SO4 can vis-a-vis an even stronger acid behave like a base and be protonated to H3SO4<sup>+</sup>.

The equilibrium in totally anhydrous H2SO4:

2 H2SO4 < === > H3SO4<sup>+</sup> + HSO4<sup>-</sup>

... is likely to be very left-leaning though.

[Edited on 10-2-2016 by blogfast25]

Detonationology - 10-2-2016 at 09:25

Quote: Originally posted by blogfast25  
The first point is really incorrect or at least very old fashioned.


I suppose I'll have a look at the Bronsted-Lowry thread as well to have a more lucid understanding. Thank you for your contributions.

DraconicAcid - 10-2-2016 at 09:40

Quote: Originally posted by blogfast25  

The equilibrium in totally anhydrous H2SO4:

2 H2SO4 < === > H3SO4<sup>+</sup> + HSO4<sup>-</sup>

... is likely to be very left-leaning though.


The autoionization of sulphuric acid is actually much more facile than that of most solvents. I seem to recall reading in Cotton and Wilkinson that it's about 10<sup>-4</sup>.

[Edited on 10-2-2016 by DraconicAcid]

[Edited on 10-2-2016 by DraconicAcid]

blogfast25 - 10-2-2016 at 09:56

Quote: Originally posted by DraconicAcid  

The autoionization of sulphuric acid is actually much more facile than that of most solvents. I seem to recall reading in Cotton and Wilkinson that it's about 10-4.


Did you mean 10<sup>-4</sup>?

[Edited on 10-2-2016 by blogfast25]

DraconicAcid - 10-2-2016 at 09:58

Yes, and I thought I put in the script for that.....