11819 106 AM Coordination Compounds Page 11 of 23

11819 106 am coordination compounds page 11 of 23

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11/8/19, 1’06 AM Coordination Compounds Page 11 of 23 the stand of the hotplate so that the flask sits on the plate's surface, but do not turn on the hotplate yet. Stir the solution such that the magnet spins smoothly without splashing the solution all the way up the side of the flask. If at any point you smell ammonia fumes coming from your flask, cap the flask with your cotton plug and bring it to the nearest fume hood. Clamp the separatory funnel to the stand, well above the reaction flask, and prepare a collar of cotton to be placed around its stem. Lower the separatory funnel into the mouth of the flask and loosely put the cotton collar around the funnel stem, as in Figure 3. Figure 3 - Separatory funnel setup for slow addition of H 2 O 2 Measure about 10 mL of 7.5% hydrogen peroxide ( ) from a common burette from the fume hood into a clean, medium sized test tube. Ensure the separatory funnel stopcock is in the closed position. Pour the into the separatory funnel. Open the stopcock partially so that the is slowly added to the flask: you want a slow but steady series of drops, not a stream. Continue stirring during the addition in order to aid the oxidation of the to . When all the has been added, remove the separatory funnel from the flask and clamp it to the stand but directed away from the flask. Rinse the 60 mL separatory funnel thoroughly with distilled water and drain the water through the funnel into a beaker. Discard this rinse down the drain. H 2 O 2 H 2 O 2 H 2 O 2 Co 2 + Co 3 + H 2 O 2
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11/8/19, 1’06 AM Coordination Compounds Page 12 of 23 Gently heat the solution in the Erlenmeyer flask for 3 to 5 minutes. Stir continuously until the solution turns red and the evolution of small gas bubbles has almost ceased. These come from the decomposition of to water and oxygen. Note that excessive heating will degrade your sample: if the solution becomes too hot and it is boiling rapidly, carefully raise the flask o ff of the surface – be careful, as the flask will be very hot). Re-clamp your flask at a higher position, and turn the hot plate to a lower setting. After the solution has been heated su ciently, turn o ff the hotplate and chill the Erlenmeyer flask (red solution) in the ice bath nearest your area for five minutes. Meanwhile, clamp the separatory funnel to the stand. Close the stopcock on the separatory funnel, then carefully pour the cooled solution into the separatory funnel. Keep the stir bar in the flask while pouring, by holding the magnetic retriever against the outside wall of the flask. Obtain 10 mL of concentrated hydrochloric acid in a clean, medium sized test tube. Immediately transfer the acid into the Erlenmeyer flask and replace the cotton plug. Immerse the test tube in a large beaker of water.
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