Lecture 4C - CHEM 6BL Experiments 4B-C: Iron Oxalate...

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Unformatted text preview: CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 1 Chemistry 6BL Lab/Course Schedule Chemistry 6BL Lab/Course Schedule Week of Lecture & Exam Schedule Lab Period Lab Schedule Prelab & Report Due Dates 1 Dates May 4 Midterm Exam 1 (during lecture on May 6) 1 st lab 2 nd lab Expt. 4A (isolate)/Start Expt. 4B Expt. 4B/Start Expt. 4C Expt. 3 Report Prelabs Expts. 4B-C Experiment 4A: Fe Experiment 4A: Fe-oxalate Product oxalate Product Fe(NH 4 ) 2 (SO 4 ) 2 6H 2 O Fe 2+ + 2 SO 4 2- = 4- 2 K w [Fe x (C 2 O 4 ) y ]zH 2 O 2 NH 4 + = 2+ K + Fe 3+ C 2 O 4 2- Inorganic Complex Analysis Inorganic Complex Analysis Complex product now analyzed for stoichiometry Analysis of K w [Fe x (C 2 O 4 ) y ]zH 2 O 3 First step: Determine amount of C 2 O 4 2- (y) Second step:Determine amount of Fe 3+ (x) Third step: Use ratio of Fe 3+ : C 2 O 4 2- to determine amount of K + (w) Fourth step: Use (K+Fe+C 2 O 4 ) to get H 2 O (z) CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 2 Experiment 4B: C Experiment 4B: C 2 O 4 2- Analysis Analysis First step: Determine amount of C 2 O 4 2- Need to react C 2 O 4 2- with a known (stoichiometric) amount of a known 4 (stoichiometric) amount of a known Experiment 4B uses titration w/ a buret Titrations Redox titrations ( Experiment #4B ) Acid-Base titrations ( Experiment #2 ) Redox Titration in Experiment 4B Redox Titration in Experiment 4B Titrant : Known concentration oxidizing agent KMnO 4 Analyte : Known mass Starting Volume Ending 5 Analyte : Known mass of unknown Fe-oxalate complex to determine C 2 O 4 2- Indicator : KMnO 4 acts as its own indicator Volume Titrant Analyte Redox Titration in Experiment 4B Redox Titration in Experiment 4B Mn VII O 4 + C III 2 O 4 2- purple 6 Mn VII O 4 + C IV O 2 + e Mn 2+ + CO 2 clear CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 3 Redox Titration in Experiment 4B Redox Titration in Experiment 4B Balance reaction equation: count e- Mn 7+ Mn 2+ 7 Needs 5 electrons [(C 3+ ) 2 O 4 ] 2- 2 (C 4+ )O 2 Yields 2 electrons Need least common multiple of 2 and 5 Redox Titration in Experiment 4B Redox Titration in Experiment 4B Balance reaction equation: Need least common multiple of 2 and 5 8 2 Mn 7+ + 10 e 2 Mn 2+ Needs 10 10 electrons 5 [(C 3+ ) 2 O 4 ] 2- 10 (C 4+ )O 2 + 10 e Yields 10 10 electrons Redox Titration in Experiment 4B Redox Titration in Experiment 4B Redox reaction involves two half- reactions: 5 C 2 O 4 2- 10 CO 2 + 10 e (ox) 9 2 Mn 7+ + 10 e 2 Mn 2+ (red) 2 Mn 7+ + 5 C 2 O 4 2- 2 Mn 2+ + 10 CO 2 Electrons cancel leaving full equation CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 4 Example: Weight % by Redox Titration Example: Weight % by Redox Titration A 0.0874 g sample containing BrA 0....
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Lecture 4C - CHEM 6BL Experiments 4B-C: Iron Oxalate...

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