1 Post- + Pre-Lab Answer Keys

1 Post- + Pre-Lab Answer Keys - Standard deviation ( ) =...

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1 ANSWER KEY: EXPERIMENT #1 - Gravimetric Analysis PRE-LAB QUESTIONS: 1. (2 points) 3 OxH 3 Ox + 3 H + Al 3+ + 3 Ox Al(Ox) 3 (s) 2. (1 point) 0.01 M should be reported as 0.01000 M (4 sig. figs). 3. (1 point) The “limiting reagent” (i.e. the limiting molar reagent) determines the quantity of product formed . F o r Experiment #1 , the limiting reagent is Al (i.e. Al 3+ ), as this is the target ion for precipitation. 4. (2 points) 0.001675 excess moles of Ox are added. 5. (1 point) As the p H is lowered (say, below 4), the oxinate ion is increasingly tied up in the protonated form, making it unavailable for precipitation. Meanwhile, at high p H (say, above 8), the Al 3+ ions react with OH to form the [Al(OH) 4 ] complex ion. 6. (1 point)
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Unformatted text preview: Standard deviation ( ) = 2.7 2 = 5.4 (w/ sig figs !) 7. (1 point) The QC for 3 trials is 0.94 , and as Q = 0.950 > QC, a 4th trial should be done . 8. (1 points) Molarity of Ag + = 1.208 M Ag + 9. (0 points) For MSDSs: - choose Lab & Lecture Courses http://chem-courses.ucsd.edu/- choose Undergraduate Lab Courses and Information http://www-chem.ucsd.edu/academic/courses_labs.cfm- choose MSDS access from UCSD computers (or for non-UCSD , if off-campus) http://www.actiocms.com/chemquik/mainpage.cfm POST-LAB QUESTIONS: 1. (1 point) 36.7 g of O. 2. (2 points) 84.70 wt% SrCO 3 3. (2 points) YBa 2 Cu 3 O 6.5 . 4. (3 points) 57.33 wt% KClO 3 (and 42.67 wt% NaCl ). 5. (2 points) C 6 H 12 O 6 ....
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