HI EXPERT! Please answer all parts: a) The Shape of a Redox Titration Curve: Cal

Question

HI EXPERT!

Please answer all parts:

a) The Shape of a Redox Titration Curve: Calculate the potential for a redox titration when 50.00 mL of 0.100 M Co3+ is titrated with 50.00 mL of 0.110 M MnO42- . The potential is measured against the Ag-AgCl reference electrode, E = 0.197 V.

Co3+ + e- Co2+        Eo = 1.92 V
MnO-4 + e- MnO42- Eo = 0.56 V

b) Oxidation with Potassium Permanganate: A permanganate solution is prepared by dissolving 20.0123 g KMnO4 in 500 mL of distilled water and boiled for 1 hour to remove any organic material. Following sintered-glass filtration, the solution is quantitatively transferred to a 1.0 L volumetric flask and diluted to volume with distilled water. The permanganate solution was titrated against 0.1023 M oxalic acid prepared in sulfuric acid solution. A 50.00 mL aliquot of oxalic acid solution required 16.68 mL of permanganate solution. A titration blank required 0.04 mL of permanganate. What is the permanganate molarity?

5 H2C2O4 + 2 MnO4- + 6 H+ 10 CO2 + 2Mn2+ + 8H2O

c) Oxidation with Ce4+ : The percent purity of a malonic acid reagent must be calculated. A student weighs out 0.1511 grams of malonic acid, CH2(CO2H)2, and quantitatively transfers the solid to a 250 mL Erlenmeyer flask. To the flask 50.00 mL of distilled water is added to dissolve the malonic acid. After dissolution, the student uses a 50 mL volumetric pipet to add 50 mL of 0.200 M Ce4+, which is allowed to react with the malonic acid. After complete reaction, the excess Ce4+ is back titrated with 14.58 mL of 0.100 M Fe2+ solution. Calculate the percent purity malonic acid.

CH2(CO2H)2 + 2 H2O + 6 Ce4+ 2 CO2 + HCO2H + 6 Ce3+ + 6 H+ ;  Ce4+ + Fe2+ Ce3+ + Fe3+

d) Oxidation with Potassium Dichromate: A student is given the assignment to determine the mass iron in a brand of women’s vitamins. He begins by taking four vitamin tablets, grinding the tablets into a fine powder to undergo the necessary sample preparation to free all iron from the sample matrix and to reduce all iron to the +2 state. The resulting Fe2+ solution is transferred to a 250 mL volumetric flask and diluted to volume with distilled water. A 50 mL aliquot of the sample requires 42.98 mL of 1.00 x 103 M Cr2O72-Calculate the mg Fe per tablet.

Cr2O72- + 6 Fe2+ + 14 H+    2 Cr3+ + 6 Fe3+ + 7 H2O

e) A 50.00 mL aliquot of a water sample is reacted with excess potassium iodide in acidic solution to generate I3-. Carbon dioxide is bubbled through the solution to remove nitrogen monoxide generated. The water sample is transferred to a 500 mL volumetric flask and diluted to volume. A 50.00 mL aliquot is then titrated against 1.092 x 104 M thiosulfate, requiring 15.48 mL to reach the starch end point. What is the NO2- concentration in ppm? Assume solution density of 1.000 g/mL.

2HNO2 + 2H+ + 3I- 2NO + I3- + 2H2O;   I3- + 2S2O32-    3I- + S4O62-

Explanation / Answer

5 H2C2O4 + 2 MnO4- + 6 H+ 10 CO2 + 2Mn2+ + 8H2O

0.1023 M x 50 ml = 16.64 x N2

                     N2 = 0.3074 x 2/5 = 0.1229 M

permanganate molarity = 0.1229 M

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