exp1prelabanswerkey

exp1prelabanswerkey - + (aq) + Ox (aq) As the p H is...

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Dr. S. Berniolles, Page 1 of 1 CHEM 6BL PRELAB/POSTLAB ANSWER KEY EXPERIMENT #1: GRAVIMETRIC ANALYSIS ( 20 Points) PRELAB ANSWER KEY: 1. (1 point) 3 OxH 3 Ox + 3 H + Al 3+ + 3 Ox Al(Ox) 3 (s) 2. (1 point) Answers should be reported to four significant figures . As a result, 0.01 M should be reported as 0.01000 M (four sig. figs). 3. (1 point) The “limiting reagent” determines the quantity of product formed . In Experiment #1, the limiting reagent is Al (i.e., Al 3+ ) as this is the target ion for precipitation. 4. (2 points) 0.00168 excess moles Ox are added . 5. (1 point) OxH(aq) H
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Unformatted text preview: + (aq) + Ox (aq) As the p H is lowered (i.e., pH < 4), the oxinate ion is increasingly tied up in the protonated form, making it unavailable for precipitation. Meanwhile, at high p H (i.e., pH > 8), Al 3+ ions react with OH ions to form the [Al(OH) 4 ] complex ion. 6. (1 point) 89.2, 87.6, 91.3, 86.4, 93.0 (Note: this is most easily done in Excel) Average = 89.5 Standard deviation ( ) = 2.7 2 = 5.4 (w/ sig figs !) 7. (2 points) From Q-test: a 4th trial should be done . 8. (1 point) 1.208 M 9. (0 point) See MSDS Information...
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