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Posted: Thu Dec 01, 2016 11:59 pm
Will there be questions on indicators on the final?
Posted: Fri Dec 02, 2016 10:09 am
The other day in class Dr. Lavelle mentioned that the big idea of indicators is that the best indicators to use are the ones that have an end point that equals the stoichiometric point of a titration. There is a HW problem in chapter 13 that has us find the range for pH of indicators for a given pH. In that case, it is just +/- 1 of the pH. I do not know whether there will be a problem like this on the final, but as long as you understand this main concept you should be able to answer any questions about indicators.
Posted: Fri Dec 02, 2016 10:22 am
It is probably a good idea to remember that indicators are weak acids that give a strong color change with pH. The popular indicator phenolphthalein in acid appears colorless, however in base appears pink. The H+ release results in a structural change so light is absorbed differently. The color change for this example occurs when pH=pKIn. A good indicator has an end point = stoichiometric point. Hope this helps.
Posted: Fri Dec 02, 2016 7:00 pm
During the review session today, he went over them, so it might be useful to know them.