Exp9Redox Rxn.pdf - Experiment 9 Oxidation-Reduction Reaction Pre-laboratory Questions Name Hyo Sun Kim Lab Section CHEM 152 D2 Date 1 Why are you told

Exp9Redox Rxn.pdf - Experiment 9 Oxidation-Reduction...

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Experiment 9 Oxidation-Reduction Reaction Pre-laboratory Questions Name: Hyo Sun Kim Lab Section: CHEM 152 D2 Date: 5/2/20 1. Why are you told in this experiment to read the volume of the KMnO 4 solution from the top of the meniscus in the burette and not from the bottom, as is usual? : Because when the burette is filled with KMnO4 solution, it is not possible to read the bottom of the meniscus because of its dark purple color: instead always read the volume from the top of the meniscus. 2. Why is the addition of an indicator unnecessary in this experiment? : No indicator is required because dark purple KMnO4 solution will be titrated into colorless Na2C2O4 solution. When the equivalence point is reached Na2C2O4 has been completely consumed by the added KMnO4. It will be indicated by a pale pink endpoint. 3. According to the redox reaction in equation 1 of the Introduction, which reactant is oxidized and which reactant is reduced? Which is the oxidizing agent and which is the reducing agent? Reduction half reaction : MnO4 - + 8H - + 5e - → Mn 2+ + 4H2O ( MnO4 - Oxidizing agent) Oxidation half reaction : C2O4 2 - 2 e - + 2 CO2 ( C2O4 2 - Reducing agent) 4. Write a balanced equation for the redox reaction between Fe 2+ and Cr 2 O 7 2 in aqueous acidic solution. Show all the steps of your method. (Refer to equations 2-4 in the Introduction.) Reduction Fe 2+ + Cr 2 O 7 2 Fe 3+ + Cr 3+ Oxidation 1) Fe 2+ Fe 3+ Cr 2 O 7 2 Cr 3+ 2)Cr 2 O 7 2 2Cr 3+ Fe 2+ Fe 3+
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5. The redox reaction between KMnO 4 and Na 2 C 2 O 4 is shown in equation 1 of the Introduction. A solution of KMnO 4 is titrated into 15.0 mL of Na 2 C 2 O 4 until the solution turns light pink. The concentration of the Na 2 C 2 O 4 is 0.75 N, and the volume of the potassium permanganate added is 16.7 mL. Calculate the normality of the KMnO 4 solution. N1V1= N2V2 N1x 0.0167=0.75x 0.015 N1=0.674 N 6. 14.6 mL of 0.15 N KMnO 4 solution was added to completely oxidize the sodium oxalate in a 0.50 g mixture of Na 2 C 2 O 4 and NaCl. (NaCl does not react with KMnO 4 .) Calculate the mass percent of Na 2 C 2 O 4 in the mixture.
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Experiment 9 Oxidation-Reduction Reaction Data Sheet Name: Hyo Sun Kim Lab Section: CHEM152 D2 1. Mass of Na
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