Coordination Chemistry 2 Overview Getting Started Techniques Procedure FAQ Full Lab Manual Introduction & Goals Chemistry & Background Key Questions Prelab Problems Safety Procedure In Your Write-up Experiments Index ChemLab Home		FAQ Index Question 1 What is the path length of the cuvet used in the Spec 20? Question 2 For prelab problem 3, it says to calculate a percent mass of cobalt in a sample but it doesn't give us the mass of the sample. Don't we need this information to complete the problem? Question 3 How can I tell what contributes the most to the uncertainty in my final results? Submissions Submit a question or an answer to the FAQ Questions & Answers Question 1 What is the path length of the cuvet used in the Spec 20? Professor Milde The pathlength is 1.17 cm, for a round cuvet used in a Spec 20. Be sure you are using a cuvet, not a test tube. Question 2 For prelab problem 3, it says to calculate a percent mass of cobalt in a sample but it doesn't give us the mass of the sample. Don't we need this information to complete the problem? Professor Milde The problem asks you to calculate the % cobalt by mass in a pure sample of [Co(NH3)5 (H2O)][NO3]3. It doesn't matter how much of the material you have in the sample, it will have the same % cobalt, by mass, if it is pure. You can assume a convenient mass, like 100 g, to calculate the % cobalt by mass. The early chapters of your textbook, back in the first week of Chem 5, may have an example of this type of problem. Question 3 How can I tell what contributes the most to the uncertainty in my final results? Professor Milde For the Colorimetric Analysis, you will compare the relative uncertainty of each contributing measurement. You will compare, for example, the relative uncertainties of the volume measurement with a 25 mL volumetric flask and the mass measurement with the analytical balance. The measurement or result with the largest relative uncertainty will make the greatest contribution to the uncertainty in the final result. For the gravimetric analysis, you will propagate the uncertainty from the analytical balance. Since all the measurements are with the same instrument, you cannont compare the uncertainty resulting from different techniques; however, you can compare the relative uncertainties of each result and think about how to reduce them. Submissions Submit to the FAQ You can submit either a question or an answer to a question about this week's experiment. Your submission will be mailed to the site editor, who will respond to you directly and also add your submission to the FAQ page. Having trouble with the submission procedure? Check your Kerberos installation. If you lose the FAQ Submission window it may be hidden behind another browser window.
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