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Determination of Oxalate by Titration

Determination of Oxalate by Titration . Lab 9 . Outline. Purpose Redox Reaction Procedure Calculation Sequence Glassware Setup Safety Concerns Waste Next Lab Reminder. Purpose. Analyze three unknown samples for oxalate via titration.

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Determination of Oxalate by Titration

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  1. Determination of Oxalate by Titration Lab 9

  2. Outline • Purpose • Redox Reaction • Procedure • Calculation Sequence • Glassware Setup • Safety Concerns • Waste • Next Lab Reminder

  3. Purpose • Analyze three unknown samples for oxalate via titration. • Compare the analytical results of your redox reactions with the percent oxalate in three known compounds. • Identify the unknowns. • Gain experience in completing a titration without the use of a formal indicator.

  4. Redox Reactions Half reaction for the oxidation of C2O42-: C2O42-(aq) 2CO2(g) + 2e- Half reaction for the reduction of Mn7+: 8H+(aq) + MnO4-(aq) + 5e- Mn2+(aq) + 4H2O(l) Complete reaction: 16H+(aq) + 5C2O42-(aq) + 2MnO4-(aq) 10CO2(g) + 8H2O(l) + 2Mn2+(aq)

  5. Procedure • Start off with a known mass of unknown oxalate compound. • Determine the moles of oxalate in the unknown by performing a titration with permanganate. • At the point where all the oxalate has reacted with the permanganate we are adding by way of the buret, we see a color change from yellow to light pink. • This end point is indicative of passing the equivalence point slightly. An end point error is introduced and needs to be minimized as much as possible. • From the known concentration and measured volume of permanganate added, we calculate the moles of oxalate, keeping in mind our stoichiometric ratio given by the complete reaction (2:5).

  6. Calculation Sequence Sample calculations are on pp. 220 and 221 • Percent oxalate in your “known” compounds • Moles of permanganate • Moles of oxalate • Mass of oxalate • Percent oxalate present by mass • Percent error (experimental values compared to “known” values)

  7. Glassware Setup

  8. Safety Concerns • Reagents: • Oxalate salts • Potassium permanganate • Sulfuric acid • Sodium meta-bisulfite • Inhalation: • Poisonous! Nervousness, cramps, CNS depression, burns / irritation to respiratory tract, irritation of nose and throat, difficulty breathing, lung edema, damage to mucosa, coughing, shortness of breath, allergic reaction. • Ingestion: • Poisonous! Burns of the throat, mouth and stomach, nausea, vomiting, abdominal pain, edema, hypotension, circulatory collapse, gastric irritation, asthma, diarrhea, death. • Skin Contact: • Redness, itching, pain, burning, blurred vision, circulatory collapse, irritation, death. • Eye Contact: • Irritation, redness, pain, irreversible eye damage.

  9. Waste • Oxalate solid goes in the garbage. • Pink, yellow and orange solutions must be disposed in the acid waste container in the fume hood. • Purple solutions must go in the permanganate waste container in the fume hood. • Small quantities of excess H2SO4can be used in your experiment.

  10. Next Week – Lab 9 continued • Submit reports. In 2 Weeks – Lab 11 • Come prepared.

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