Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: jsmith613 on August 31, 2009, 11:24:02 AM
-
why do chlorine atoms in acid molecules lower the pH so much?
-
What type of acids are you working with? And what specific acid, for that matter, are you concerned with?
If its something like Hydrochloric Acid, HCl, then the answer is because its a strong acid that dissociates almost completely in solution.
-
I think the question was moore in organic carboxylic acids when the presence of the chlorie decreses pH.
-
What type of acids are you working with? And what specific acid, for that matter, are you concerned with?
If its something like Hydrochloric Acid, HCl, then the answer is because its a strong acid that dissociates almost completely in solution.
Yes i was referring to HCl, but how does it dissociate due to Cl2
-
Yes i was referring to HCl, but how does it dissociate due to Cl2
Please elaborate, what you wrote doesn't make any sense.
-
Please elaborate, what you wrote doesn't make any sense.
What I mean is bstapes99 said If its something like Hydrochloric Acid, HCl, then the answer is because its a strong acid that dissociates almost completely in solution.
And what I am saying is, what has that got to do with the presence of Chlorine as my questions is why do chlorine atoms in acid molecules lower the pH so much? [/quoute]
-
You're still not making all that much sense. The (Bronsted) acidity of any compound is ruled by the stability of the corresponding anion, and there is a clear correlation between acidity and the presence of electronegative elements (or functional groups).
Hydrochloric acid is a strong acid because its dissociation yields a very stable chloride anion. Cl2 is actually completely unrelated, as its dissociation (in water) will not result in the formation of hydrochloric acid, but hypochlorous acid.
-
You're still not making all that much sense. The (Bronsted) acidity of any compound is ruled by the stability of the corresponding anion, and there is a clear correlation between acidity and the presence of electronegative elements (or functional groups).
Hydrochloric acid is a strong acid because its dissociation yields a very stable chloride anion. Cl2 is actually completely unrelated, as its dissociation (in water) will not result in the formation of hydrochloric acid, but hypochlorous acid.
but this does not answer the original quesiton. What is it about Cl that causes it to give Acids such as HCl such a low pH
-
First of all, chlorine only gives one acid such as HCl, and that is HCl itself. It seems like you want to have a talk about acidity, which is perfectly fine, but refuse to consider anything but HCl.
Second, I'll give you what you want. HCl is a strong acid because chlorine is a very electronegative element (second only to fluorine), which means that the dissociation of HCl gives a very stable chloride anion. Other effects to consider are bond strength (which is rather small) and hydration energy (which measures the stabilization of the ions). There's more to it, but I'm afraid it will be too difficult for you.
Either way, if you really want to know why HCl is a very strong acid, you will have to compare it to other acids to understand all possible influences.
-
First of all, chlorine only gives one acid such as HCl, and that is HCl itself. It seems like you want to have a talk about acidity, which is perfectly fine, but refuse to consider anything but HCl.
Second, I'll give you what you want. HCl is a strong acid because chlorine is a very electronegative element (second only to fluorine), which means that the dissociation of HCl gives a very stable chloride anion. Other effects to consider are bond strength (which is rather small) and hydration energy (which measures the stabilization of the ions). There's more to it, but I'm afraid it will be too difficult for you.
Either way, if you really want to know why HCl is a very strong acid, you will have to compare it to other acids to understand all possible influences.
So if i compare it to something like H2SO4 then what is the difference? thanks
-
So if i compare it to something like H2SO4 then what is the difference? thanks
As well as H2SO4 compared to HCl, what about HCLO compared to HCL
-
If you want to compare them, find a chart of the strength of these acids (also known as the acid dissociation, or Ka). I have a cheat sheet for my class that says there are 8 strong acids and the rest are weak. By the way, its HCl not HCL (the L isnt capitalized).
Also, just in case you don't understand why the Cl is important, HCl dissociates into H+ and Cl- ions. Because the original bond between the two was weak, this happens to most of the HCl. And all we're worrying about is the concentration of H+ ions (which is the same as the concentration of Cl- ions). Sorry if I'm repeating what the others have said.
-
If you want to compare them, find a chart of the strength of these acids (also known as the acid dissociation, or Ka). I have a cheat sheet for my class that says there are 8 strong acids and the rest are weak. By the way, its HCl not HCL (the L isnt capitalized).
Also, just in case you don't understand why the Cl is important, HCl dissociates into H+ and Cl- ions. Because the original bond between the two was weak, this happens to most of the HCl. And all we're worrying about is the concentration of H+ ions (which is the same as the concentration of Cl- ions). Sorry if I'm repeating what the others have said.
I understand that, but how do the Chlorine atoms make the pH so low. H+ ions cause something to be acidic but how do the Cl atoms themselves lower the pH (or is it just they make the molecules easy to dissociate)
-
how do the Cl atoms themselves lower the pH
They don't.
(or is it just they make the molecules easy to dissociate)
This is much closer.
-
This is much closer.
Does that mean it is correct
-
Ya, pretty much, I guess