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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: lrarava on March 22, 2006, 06:45:22 PM

Title: Titration: Acid/Base
Post by: lrarava on March 22, 2006, 06:45:22 PM

Hi I am new here.  ;D But I cannot figure out the reason for cannot add indicator for neutralising acid and base when using titration experiment.  ??? (Even though titration is not the best analysis method, but back titration) Can anyone please explain it?
Also, end point usually appears when indicator change colour, so if the experiment cannot use indicator for weak acid and weak base, is it still possible to find end point?

Title: Re:Titration: Acid/Base
Post by: mike on March 22, 2006, 07:02:19 PM

Could you use a pH metre?

Title: Re:Titration: Acid/Base
Post by: cathy on March 23, 2006, 08:30:28 AM

when you are doing titration without an indicator,
you can find the end point:
1. by change in pH value by using a pH meter
2. by change in temperature
3. by change in electrical conductivity
here are some example in my note...
http://hk.geocities.com/urabbit_hole/01.JPG (http://hk.geocities.com/urabbit_hole/01.JPG)
http://hk.geocities.com/urabbit_hole/02.JPG (http://hk.geocities.com/urabbit_hole/02.JPG)
Hope this can help you^^

Title: Re:Titration: Acid/Base
Post by: lrarava on March 24, 2006, 02:02:32 AM

thank you for helping.

Beside what is the reason that cannot add indicator to weak acid and weak base titration?
Is it because it is hard to find an indicator at the range that weak acid and weak base become nutrual, but if so why indicator can be used for strong acid and strong base neturlisation?

Title: Re:Titration: Acid/Base
Post by: cathy on March 24, 2006, 01:06:57 PM

actually, weak acid and weak will not have a centain result...
so we can't decide what indictor should be use...

http://hk.geocities.com/urabbit_hole/03.JPG

Title: Re:Titration: Acid/Base
Post by: lrarava on March 27, 2006, 12:16:20 AM

thank you