How acidic indicators work

authormessageguest






Posted: May 30, 2005 8:02 PM Title: How do indicators work ???

Hello.
I need an answer to the following question:
How do indicators work ???
I have now caught that with your definitions;

"How an acid-base indicator works
Why does the indicator change color?
The molecules of the acid-base indicators are themselves weak acids or bases, which means that they can give off protons. The indicator acid molecule is simply referred to as HInd. After releasing a proton, Ind, the so-called corresponding indicator base, remains.

The protolysis equilibrium for the release or release of a proton in an aqueous indicator solution is the following:

HInd (aq) + H2O (l)

The indicator molecule can therefore release a proton but also take it up again. With a high concentration of H3O + ions (i.e. in an acidic solution), the reaction to the left takes place more intensely (shift of the equilibrium to the left side), whereby the concentration of HInd (indicator acid) is greater than the concentration of Ind- (indicator base ). With a very low concentration of H3O + ions (i.e. in an alkaline solution), the reaction to the right takes place more strongly (shift of the equilibrium to the right side), whereby the concentration of Ind- is greater than the concentration HInd.

The actual effect of the indicator is based on the fact that the connection HInd has a different color than Ind-. In acidic solution the concentration of HInd predominates, so that the solution takes on the corresponding color. If the pH is increased, the concentration of Ind- rises, while the concentration of HInd decreases, until the former predominates and the solution takes on the color of Ind-.

The different colors of protonated and non-protonated dye molecules are referred to as halochromy.

How an acid-base indicator works
Why does the indicator change color?
The molecules of the acid-base indicators are themselves weak acids or bases, which means that they can give off protons. The indicator acid molecule is simply referred to as HInd. After releasing a proton, Ind, the so-called corresponding indicator base, remains.

The equilibrium of protolysis for releasing or releasing a proton in an aqueous indicator solution is as follows:

HInd (aq) + H2O (l)

The indicator molecule can therefore release a proton but also take it up again. With a high concentration of H3O + ions (i.e. in an acidic solution), the reaction to the left takes place more intensely (shift of the equilibrium to the left side), whereby the concentration of HInd (indicator acid) is greater than the concentration of Ind- (indicator base ). With a very low concentration of H3O + ions (i.e. in an alkaline solution), the reaction to the right takes place more strongly (shift of the equilibrium to the right side), whereby the concentration of Ind- is greater than the concentration HInd.

The actual effect of the indicator is based on the fact that the connection HInd has a different color than Ind-. In acidic solution the concentration of HInd predominates, so that the solution takes on the corresponding color. If the pH-value is increased, the concentration of Ind- rises, while the concentration of HInd decreases, until the former predominates and the solution takes on the color of Ind-.

The different colors of protonated and non-protonated dye molecules are referred to as halochromy. "



So now I'm 9th grade gym and not a chemistry professor!
Can someone briefly explain this to me, or bring it down to a language level that is understandable for me ???

Would be really nice !!!!
Thanks in advance!!!
MFG Phew
guest






Posted: May 30, 2005 10:10 PM Subject:

hey!
Absolutely need an answer to the question; How do indicators work ???
You don't have to read through the whole text, it's just a quote from your side that I don't understand!
Please give a short, simple answer!
I need an answer by tomorrow evening!

Would be really great !!!!
DDDDDAAAANNNNKKKKEEE !!!!!!
MFG Phew
EtOH



Registration date: 10/22/2004
Posts: 3367
Place of residence: leverkusen / cologne
Posted: May 30, 2005 10:35 PM Subject:

actually the explanation is there in full ...
what exactly do you not understand about it?
what kind of acid-base-definitions do you know from your class? what do you know about pH?
_________________
Two things are infinite. The universe and the human stupidity; only I'm not quite sure about the universe! (Albert Einstein)
guest






Posted: May 31, 2005 2:53 PM Subject:

So:
We always checked the pH value with Untitestpaspier or universal indicator solution.
The reason why it turns red was the H + ions.
But as far as I don't know, how indicators work directly we have not yet known!

The text is too high for me just a few examples:
corresponding indicator base
Protolysis equilibrium
HInd ..... I could go on with that now.

Can't you just explain how it works?!?!
And list 2-3 other indicators!

VVVVIIEEELLLEEEENNNN DDDAAAANNKKK in advance !!
MFG Phew !!!
Cyrion



Registration date: 11/10/2004
Posts: 4719
Place of residence: Kölle
Posted: May 31, 2005 3:27 PM Subject:

Acid-base indicators are weak acids (or bases) that have a different color depending on whether they are protonated or deprotonated.
guest






Posted: May 31, 2005 3:45 PM Title:

So is my indicator an acid or a base ??
and if you either enrich it with H + ions or OH groups, it turns red or blue ?!
Is my unitest paper and universal indicator solution a weak base or acidic?

can you please list 2-3 other indicators!
Thanks!!
Cyrion



Registration date: 11/10/2004
Posts: 4719
Place of residence: Kölle
Posted: May 31, 2005 4:18 PM Subject:

Universal tests are a mixture of different indicators.

If you browse the net, you will find more indicators than you need ...
guest






Posted: May 31, 2005 4:27 PM Subject:

THANKS!!
Is that true what I wrote above ???

"So is my indicator an acid or a base ??
and if you either enrich it with H + ions or OH groups, it turns red or blue ?! "


Is my unitest paper and universal indicator solution a weak base or acid ???
Cyrion



Registration date: 11/10/2004
Posts: 4719
Place of residence: Kölle
Posted: May 31, 2005 4:59 PM Subject:

You stick with it in H +, then the indicator was previously a base and then an acid. Or you take it away from him again. Then it was the acid and it becomes the base.
guest






Posted: May 31, 2005 5:13 PM Subject:

then I would need 2 indicators to get red and blue?
and my universal indicator can do both because it is a mixture of different indicators !! is that correct?
EtOH



Registration date: 10/22/2004
Posts: 3367
Place of residence: leverkusen / cologne
Posted: May 31, 2005 5:30 PM Title:

universal indicator is, as cyrion said, a mixture of several different indicators so that you get all the color gradations ...
a single indicator has only two colors ... one color in the protonated form HIn (where In stands for indicator and the H means that the proton is on) and another color in the deprotonated form ... In- (there is now a proton H+ split off, that's why In remains- left...
_________________
Two things are infinite. The universe and the human stupidity; only I'm not quite sure about the universe! (Albert Einstein)