lecture on exp 4b-c

lecture on exp 4b-c - CHEM 6BL Experiments 4B-C: Iron...

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CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 1 Experiment 4A Synthesis Fe(NH 4 ) 2 (SO 4 ) 2 ·6H 2 O Fe 2+ + 2 SO 4 2- = 4- 1 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 Synthesis Product 2 EXAM S EXAM #1 IN LECTURE- July 19 EXAM #2 (Final) IN LECTURE- July 28 No other final exam given in this class 3 Typically 15 Multiple-choice questions Exam 1 Based on Experiments # 0-4A Lecture Topics Lab Manual Procedures Pre-/Post-Lab Questions Calculations in Lab
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CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 2 Inorganic Complex Analysis Complex product now analyzed for stoichiometry Analysis of K w [Fe x (C 2 O 4 ) y ]·zH 2 O 4 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) Experiment 4B: C 2 O 4 2- 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” 5 (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 Titrant : Known concentration oxidizing agent KMnO 4 Analyte : Known mass Starting Volume Ending 6 : 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
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CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 3 Redox Titration in Experiment 4B Mn VII O 4 + C III 2 O 4 2- purple 7 Mn VII O 4 + C IV O 2 + e Mn 2+ + CO 2 clear Redox Titration in Experiment 4B Balance reaction equation: count e- Mn 7+ Mn 2+ 8 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 Balance reaction equation: Need least common multiple of 2 and 5 9 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 electrons
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CHEM 6BL Experiments 4B-C: Iron Oxalate Complex Analysis Instructor: Dr. S. Berniolles Page 4 Redox Titration in Experiment 4B Redox reaction involves two half- reactions: 5 C 2 O 4 2- 10 CO 2 + 10 e (ox) 10 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 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. Wha is the weigh % B ? 11 What is the weight % Br First - Determine reaction equation: Br - + 6 OH - Br V O 3 - + 3 H 2 O + 6 e (ox) 2 Mn VII O 4 - + 4 H 2 O + 6 e 2 Mn IV O 2 + 8 OH - (red) 2 Mn VII O 4 - + Br - + H 2 O 2 Mn IV O 2 + Br V O 3 + 2 OH - 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 12 solution. What is the weight % Br
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lecture on exp 4b-c - CHEM 6BL Experiments 4B-C: Iron...

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