lecture 4c

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

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CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 1 1 Chemistry 6BL Lab/Course Schedule Chemistry 6BL Lab/Course Schedule Prelab Expt. 4A Expt. 3 Report Prelabs 4B-C Expt. 4A (synthesis) Expt. 4A (isolate)/Start Expt. 4B Expt. 4B / Start Expt. 4C (Parts I-II) 1 st lab 2 nd lab 1 st lab ------------ Midterm Oct. 27 Nov. 3 Prelab & Report Due Dates Lab Schedule Lab Period Lecture & Exam Schedule Date 2 Experiment 4A: Fe Experiment 4A: Fe -oxalate Product oxalate Product Fe(NH 4 ) 2 (SO 4 ) 2 ·6H 2 O K w [Fe x (C 2 O 4 ) y ]·zH 2 O Fe 2+ 2 × NH 4 + = 2+ 2 × SO 4 2- = 4- K + Fe 3+ C 2 O 4 2- 3 Inorganic Complex Analysis z Complex product now analyzed for stoichiometry z Analysis of K w [Fe x (C 2 O 4 ) y ]·zH 2 O 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)
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CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 2 4 Experiment 4B: C Experiment 4B: C 2 O 4 2- Analysis Analysis z 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” z Experiment 4B uses titration w/ a buret z Titrations Redox titrations ( Experiment #4B ) Acid-Base titrations ( Experiment #2 ) 5 Redox Titration in Experiment 4B Redox Titration in Experiment 4B z Titrant : Known concentration oxidizing agent KMnO 4 z Analyte : Known mass of unknown Fe-oxalate complex to determine C 2 O 4 2- z Indicator : KMnO 4 acts as its own indicator Starting Volume Ending Volume Titrant Analyte 6 Redox Titration in Experiment 4B Redox Titration in Experiment 4B Mn VII O 4 + C III 2 O 4 2- Mn VII O 4 + C IV O 2 + e Mn 2+ + CO 2 purple clear
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CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 3 7 Redox Titration in Experiment 4B Redox Titration in Experiment 4B z Balance reaction equation: count e- Mn 7+ Mn 2+ 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 8 Redox Titration in Experiment 4B Redox Titration in Experiment 4B z Balance reaction equation: Need least common multiple of 2 and 5 2 Mn 7+ + 10 e 2 Mn 2+ Needs 10 electrons 5 [(C 3+ ) 2 O 4 ] 2- 10 (C 4+ )O 2 + 10 e Yields 10 10 electrons 9 Redox Titration in Experiment 4B Redox Titration in Experiment 4B z Redox reaction involves two half- reactions: 5 C 2 O 4 2- 10 CO 2 + 10 e (ox) 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
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CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 4 10 Example: Weight % by Redox Titration Example: Weight % by Redox Titration A 0.0874 g sample containing Br is titrated with 35.56 mL of 0.0148 M KMnO 4 to form BrO 3 & MnO 2 in basic aqueous solution.
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This note was uploaded on 05/31/2009 for the course CHEM 6BL taught by Professor Berniolles during the Spring '08 term at UCSD.

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

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