[hiuky]

Jsut wondering,

Why can methyl red be used as an indicator for acid-base titrations?

thanks

[budullewraagh]

it changes colors depending on the pH of a solution

[sisco]

It changes colour due to its interaction with the Oh- ions in an acid/base solution
The more alkaline the solution the more oh- ions and so the more interaction with the methylene red.
However when the methylene red changes colour does its absorption lines change?

[Krishnan]

Methylred is used as acid base indicator because of its sharp color change at end point especially when a weak base is used in the titration.

[pizza1512]

You could use litmus paper....




 :arrowhead:

[Kong]

When ever you are doing an acid base titration you are looking for the equivalence point.  This is the point where the number of moles of acid and base are equal.  This will help you relate an unknown quantity to a known quantity.  The equivalence point could realisically be anywhere on the pH scale.  So different indicators to different colors depending on the pH.  So depending on where your equivalence point is will determine what indicator you will want to use.  Phenolphthalien is a very popular indicator because it actually changes very close to neutral.  
   It is my estimation that indicators have been very much phased out by pH meters and will probably take one more generation to be completly eleminated.  I learned very little about them in college and a very minor occurance on the advanced placement chemistry exam.
AS