Post by Æsc Thorne on Jun 26, 2010 7:42:21 GMT -5
One morning in mid-September Aesc went into his classroom a good half an hour before his Chemistry/Alchemy class. He had a lot of complicated glassware to set up, after all. After several minutes of preparation he returned to his desk and viewed his efforts.
On each lab table was a stand holding a burette suspended above a conical flask. On the blackboard was written "Advanced Chemical Analysis - Titration" as well as the instructions for the experiment.
Aesc waited for the students to enter the classroom and settle down, then began to introduce the lesson.
"Today we're going to try a more-advanced experiment, called titration. Titration is used to very accurately determine the concentration of an unknown chemical solution by reacting it with a known amount of a known chemical, called a standard solution. In todays experiment, we're going to be using a standard solution of sodium carbonate to determine the concentration of several different solutions of acetic acid - that's the acid in vinegar.
"I want you to form groups of two students. I'll give each pair a sample of acetic acid. The concentration of each sample will be different, so each group will have to do the experiment properly themselves.
"Now, over on the side bench are pipettes filled with sodium carbonate. Each group is to take a pipette and transfer the contents into your conical flask, then add two drops of this indicator solution," he said, holding up a dropper bottle, "called phenolphthalein, which changes colour from purple to clear when the solution changes from being alkaline to being acidic."
"Once you have the phenolphthalein in your flask, start adding the acetic acid from your burette drop-by-drop. After each drop, stir the conical flask. When the purple colour disappears and does not return, that's when the titration is finished, and you'll have to take a note of how much acetic acid was required to neutralyse the sodium carbonate."
"You'll need to be very thorough - it only takes one or two extra drops of acid in your solution to make the results inaccurate. If you have any questions, come up and ask me. And I hope I don't need to tell you not to eat any of the chemicals."
((Titration's a bit advanced for first years, I know, but 9th-grade (or equivalent) chemistry was a long time ago and I can't remember much about the likely syllabus. Besides, they're all Sues and Stus and should be able to handle it. Assume there's been some other lessons in between the first one and this, in which a lot of theory about both alchemy and chemistry has been discussed))
On each lab table was a stand holding a burette suspended above a conical flask. On the blackboard was written "Advanced Chemical Analysis - Titration" as well as the instructions for the experiment.
Aesc waited for the students to enter the classroom and settle down, then began to introduce the lesson.
"Today we're going to try a more-advanced experiment, called titration. Titration is used to very accurately determine the concentration of an unknown chemical solution by reacting it with a known amount of a known chemical, called a standard solution. In todays experiment, we're going to be using a standard solution of sodium carbonate to determine the concentration of several different solutions of acetic acid - that's the acid in vinegar.
"I want you to form groups of two students. I'll give each pair a sample of acetic acid. The concentration of each sample will be different, so each group will have to do the experiment properly themselves.
"Now, over on the side bench are pipettes filled with sodium carbonate. Each group is to take a pipette and transfer the contents into your conical flask, then add two drops of this indicator solution," he said, holding up a dropper bottle, "called phenolphthalein, which changes colour from purple to clear when the solution changes from being alkaline to being acidic."
"Once you have the phenolphthalein in your flask, start adding the acetic acid from your burette drop-by-drop. After each drop, stir the conical flask. When the purple colour disappears and does not return, that's when the titration is finished, and you'll have to take a note of how much acetic acid was required to neutralyse the sodium carbonate."
"You'll need to be very thorough - it only takes one or two extra drops of acid in your solution to make the results inaccurate. If you have any questions, come up and ask me. And I hope I don't need to tell you not to eat any of the chemicals."
((Titration's a bit advanced for first years, I know, but 9th-grade (or equivalent) chemistry was a long time ago and I can't remember much about the likely syllabus. Besides, they're all Sues and Stus and should be able to handle it. Assume there's been some other lessons in between the first one and this, in which a lot of theory about both alchemy and chemistry has been discussed))
