2.054 g of macrogol monostearate (average molecular weight 706. 5) was added to a 200 ml flask and 25 ml of an ethanolic solution of potassium hydroxide (molecular weight 56.1, ca 0.5 M) was added. The sample was heated under a reflux condenser for 1 hour. The excess of alkali was then titrated with 0.5016 M hydrochloric acid using phenolphthalein solution as an indicator. The operation was repeated without the macrogol monostear
2.054 g of macrogol monostearate (average molecular weight 706. 5) was added to a 200 ml flask and 25 ml of an ethanolic solution of potassium hydroxide (molecular weight 56.1, ca 0.5 M) was added. The sample was heated under a reflux condenser for 1 hour. The excess of alkali was then titrated with 0.5016 M hydrochloric acid using phenolphthalein solution as an indicator. The operation was repeated without the macrogol monostear
Chapter13: Titrations In Analytical Chemistry
Section: Chapter Questions
Problem 13.5QAP
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Question
A 2.054 g of macrogol monostearate (average molecular weight 706. 5) was added to a 200 ml flask and 25 ml of an ethanolic solution of potassium hydroxide (molecular weight 56.1, ca 0.5 M) was added. The sample was heated under a reflux condenser for 1 hour. The excess of alkali was then titrated with 0.5016 M hydrochloric acid using phenolphthalein solution as an indicator. The operation was repeated without the macrogol monostearate.
Results
Volume of HCI required to titrate the excess alkali = 18.35 ml
Volume of HCI required to titrate the blank = 24.03 ml
Calculate the saponification value for the macrogol stearate.
Answer: Blank mg/g
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