CHEM211 Lecture Notes - Ammonium Bifluoride, Stoichiometry, Fluorine
10 May 2018
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Copper in Brass Experiment // October 2nd Lecture
❏There are 4 samples of copper and 4 of brass. Therefore the mass of each wire is
different. This means that the titration volumes will also be different.
❏Use the biocide named chloroform to kill the bacteria that loves thiosulfate.
❏Ensure to burn all nitrogen oxide off or else results will be affected.
❏Do not let solutions go dry, this will cause insoluble content resulting in you having to
restart the whole procedure!
Common Mistakes in Copper Experiment
❏Incorrect stoichiometry used in calculation for titrations.
❏Boil Copper too long → precipitate forms.
❏Boil to little → Fail to remove all nitrogen oxides.
❏Do not redissolve all Cu(OH)2 after adding ammonium bifluoride.
❏Add indicator too soon or use old indicator.
Determination of Fluoride in MouthWash by Ion-selective Electrode // October 2nd and
4th
❏Experiment is forgiving except in rinsing of pipet!
❏Electrode favours fluorine, therefore Cl- and other ions will not affect it. BUT, it does
respond to OH- therefore experiment accommodates for this error.
❏Use Nernst Equation for calculations.
❏Slope of line should be approximately -59.
❏This lab is not very precise due to systematic and random errors, therefore the error
range is a bit larger than chloride experiment.
Remaining Lecture of October 4; In class activity
Standard of Uncertainty and Confidence Intervals
❏In the Chloride experiment it is crucial that you use the standard that corresponds to the
day of titration or else data will be inaccurate.
❏If you titrated standards 1-3 and Unknown 1-3 in lab 1, and standards 4-5 and
unknown 4-5 in lab 2 you need to do the calculations using standards 1-3 and
unknown 1-3 together. Standards 4-5 and Unknowns 4-5 must be done in their
own calculations as well
❏Confidence Intervals help us detect how accurate (and confident) we can be in our
values..
❏Note: When given calibration data (Example Fluorine concentration and absorbance),
plot the data! Do not just assume without visualizing the information.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Copper in brass experiment // october 2nd lecture. There are 4 samples of copper and 4 of brass. Therefore the mass of each wire is different. This means that the titration volumes will also be different. Use the biocide named chloroform to kill the bacteria that loves thiosulfate. Ensure to burn all nitrogen oxide off or else results will be affected. Do not let solutions go dry, this will cause insoluble content resulting in you having to restart the whole procedure! Incorrect stoichiometry used in calculation for titrations. Boil copper too long precipitate forms. Boil to little fail to remove all nitrogen oxides. Do not redissolve all cu(oh)2 after adding ammonium bifluoride. Add indicator too soon or use old indicator. Determination of fluoride in mouthwash by ion-selective electrode // october 2nd and. Experiment is forgiving except in rinsing of pipet! Electrode favours fluorine, therefore cl- and other ions will not affect it.
