1. Determination of Oxalate by Titration Lab 9

2. Purpose 0 Analyze three unknown samples for oxalate via titration. 0 Compare the analytical results of your redox reactions with the percent oxalate in three known compounds. 0 Identify the unknowns. 0 Gain experience in completing a titration without the use of a formal indicator.

3. Redox Reactions Half reaction for the oxidation of C 2 O 4 2- : C 2 O 4 2- (aq)  2CO 2(g) + 2e - Half reaction for the reduction of Mn 7+ : 8H + (aq) + MnO 4 - (aq) + 5e -  Mn 2+ (aq) + 4H 2 O (l) Complete reaction: 16H + (aq) + 5C 2 O 4 2- (aq) + 2MnO 4 - (aq)  10CO 2(g) + 8H 2 O (l) + 2Mn 2+ (aq)

4. Procedure 0 Start off with a known mass of unknown oxalate compound. 0 Determine the moles of oxalate in the unknown by performing a titration with permanganate. 0 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. 0 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. 0 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).

5. Glassware Setup

6. Safety Concerns 0 Reagents:  Oxalate salts (potassium oxalate is a teratogen)  Potassium permanganate  Sulfuric acid  Sodium meta-bisulfite 0 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. 0 Ingestion:  Poisonous! Burns of the throat, mouth and stomach, nausea, vomiting, abdominal pain, edema, hypotension, circulatory collapse, gastric irritation, asthma, diarrhea, death. 0 Skin Contact:  Redness, itching, pain, burning, blurred vision, circulatory collapse, irritation, death. 0 Eye Contact:  Irritation, redness, pain, irreversible eye damage.

7. Waste 0 Excess or spilled oxalate solid goes in the oxalate solid waste container in the fume hood. 0 Pink, yellow and orange solutions must be disposed in the acid waste container in the fume hood. 0 Purple solutions must go in the permanganate waste container in the fume hood. 0 Small quantities of excess H 2 SO 4 can be used in your experiment.

8. Next Week – Lab 9 continued 0 Submit reports.