انت هنا الان : شبكة جامعة بابل > موقع الكلية > نظام التعليم الالكتروني > مشاهدة المحاضرة

Analytical Chemistry 5

الكلية كلية العلوم للبنات     القسم قسم الكيمياء     المرحلة 1
أستاذ المادة محمد حامد سعيد الدهيمي       04/01/2013 16:31:36
Analytical Chemistry
Lecture No. 5 Date :23 /12/ 2012
Dr. Mohammed Hamed
--------------------------------------------------------------------------------------------------------------------------------------
Strong acid strong base titrations
Titration curves are the graphs obtained by plotting the pH of the reaction mixture against the volume of base (or acid) added during the titration of either an acid by a base or vice versa.
A typical strong acid - strong base titration curve looks like this:


The blue curve represents the titration of 25 cm3 hydrochloric acid (0.1M) by additions of 0.1M Sodium hydroxide solution. The pH starts off at 1 and increases only very slowly at first. Near the equivalence point there is a rapid and dramatic increase in pH. This means that most indicators are suitable for carrying out ths type of titration.
The red curve represents the titration of a 25cm3 sample of sodium hyroxide (0.1M) by successive additions of 0.1M hydrochloric acid. Again a rapid inflexion is seen near the equivalence point.
Weak acid - strong base titration

The curve shows the titration of 25 cm3 ethanoic acid (0.1M) by additions of 0.1M sodium hydroxide solution. The pH starts off at 2.4 and increases steadily at first. Near the equivalence point there is a rapid increase in pH. Only indicators that change colour in the region pH 6 - 10 are suitable for carrying out this type of titration.
Phenolphthalein is the indicator of choice fopr this type of titration. It registers colourless in the acidic region and changes to red in base. The first hint of pink is taken as the end point.
Take care with phenlphthalein, as the red colour fades fairly rapidly if the solution is left standing.
Weak base strong acid titration
The red curve represents the titration of 25 cm3 ammonia (0.1M) by additions of 0.1M hydrochloric acid solution. The pH starts off near 12 and decreases steadily towards the equivalence point where there is a rapid decrease in pH. This means that only indicators that act in the acidic pH region are suitable for carrying out ths type of titration.
Methyl orange is the indicator of choice. It registers red in acid and yellow in base with the endpoint being orange.
For more information open pdf file


المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .