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Landolt Reaction - Iodine Clock Kinetics

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Landolt Reaction - Iodine Clock Kinetics Search Where to buy Germanium? Warnings & a good source - Organic Germanium Sesquioxide. Ge-132 www.chemtalk.net/ Electrochemistry Systems Autolab Potentiostat Systems for Fuel Cell and Battery Research www.metrohmusa.com Glassware For Laboratory We Have A Variety of Lab Glassware Products. Contact Us For Details! www.QualityBiolog Demonstration Experiment on Video Landolt Reaction - Iodine Clock Kinetics Objective: Effect of Concentration on the Rate of a Reaction Peter Keusch Chemicals: sodium disulfite potassium iodate ethanol starch, soluble German version conc. sulfuric acid Apparatus and glass wares: magnetic stirrer hot plate 2 magnetic stirring bars stirring bar remover 2 volumetric flasks 1000 mL volumetric flask 100 mL 2 beakers 250 mL 3 beakers 100 mL 2 beakers 50 mL beaker 10 mL 1 volumetric pipet 10 mL 2 volumetric pipets 25 mL 3 volumetric pipets 50 mL 3 pipette bulbs stop-watch Hazards and safety precautions: Sodium disulfite may cause irritation and may be harmful if swallowed. May cause allergic reaction.skin and eye irritant. Potassium iodate is harmful if swallowed. May be harmful by inhalation or through skin absorption. Irritant. Conc. sulfuric acid is highly toxic. Causes severe burns. May be fatal if swallowed. May cause cancer through inhalation. Very destructive of mucous membranes. Ethanol is highly flammable. Safety glasses and safety gloves must be worn. Suitable ventilation! Preparation of the solutions: Solution A: 1.16 g of sodium metabisulfite are dissolved in a 1000 mL volumetric flask containing deionized water. 10 mL of ethanol and 4 g of conc. sulfuric acid are added to the aqueous solution. The 1000 mL volumetric flask is made up to the mark with deionized water. Solution B: 4.3 g of potassium iodate are dissolved in a 1000 mL volumetric flask containing deionized water. The 1000 mL volumetric flask is made up to the mark. Solution C: 2 g of starch are dissolved in a 100 mL beaker containing 50 mL of boiling water. The solution is filled into a 100 mL volumetric flask. The flask is made up to the mark with deionized water. The solutions above should be freshly prepared. Experimental procedure: Beaker 1 and 2: Two 250 mL beakers are filled with a mixture of 50 mL of solution A (metabisulfite), 50 mL of dist. H2O and 10 mL of solution C (starch). Beaker 3 and 4: One 100 mL beaker is filled with 50 mL of solution B (iodate) and 50 mL of dest. H2O. Another 100 mL beaker is filled with 25 mL of solution B and 75 mL of deionized water. The solution from beaker 3 is poured into beaker 1 while stirring and afterwards solution of beaker 4 is mixed with the solution in beaker 2. Using a stop watch the reaction is timed from the moment of mixing. It is convenient to start the stop watch when one half of the reactant has been added to the sulfite solution. Results: When the two colorless solutions are mixed, there is no apparent reaction. After 11 and 22 seconds, respectively, the colorless mixture suddenly turns blue. Videoclip (Download RealPlayer .rm file) Discussion: The experiment shows the effect of the interaction between chemical reactions that have different rates that are dependent on the concentrations of the reagents involved in the reaction. Doubling the concentration increases the rate by a factor of 2. The reaction can be described by the following mechanism: Reaction step 1: ·First bisulfite reduces iodate to form iodide (Bisulfite ions are formed when metabisulfite is dissolved in water). This reaction proceeds very slowly. It is the rate determining step. Reaction step 2: ·The iodide formed is oxidized by the iodate excess under formation of iodine. Iodine reacts with starch to form a blue iodine-starch complex. The reaction proceeds fast. Reaction step 3: ·Iodine liberated is instantaneously retransformed by bisulfite to iodide. This is an "immeasurable fast" reaction. The blue starch iodine complex becomes visible after complete consumption of the bisulfite ions, since then a reduction of the iodine formed cannot take place according to equation ·(3)· any longer. The collision theory provides a successful basis for understanding the concentration effect. Doubling the concentration doubles the number of collisions, which in turn doubles how fast the reaction goes. References: Demonstration Experiment on Video Cocktail 'Old Nassau' - Modified Landolt Reaction Demonstration Experiment on Video 'One Cola and one Beer, please' - Modified Landolt Reaction Demonstration Experiment on Video Starch - widely available in many Foods Index of Lecture Experiments Search Lab Chemicals & Reagents Acids, Bases, Solvents, Stains. Since 1951 - Ships Same Day! www.rmreagents.com Laboratory Supplies Microscopes, Slides, Lab Equipment Histology and Veterinary Supplies www.GorillaScientific.com Cabinets Fixtures Hoods Labs Stainless Epoxy Trespa Free AutoCAD Drawings! www.milesco.net Demonstration Experiment on Video Belousov-Zhabotinsky-Reaction Objective: Mechanism of an Oscillating Reaction Peter Keusch Chemicals: malonic acid potassium bromate potassium bromide conc. sulfuric acid ferroin solution German version Ferroin solution: 0.35 g of ferrum sulfate heptahydrate and 0.88 g of 1.10- phenanthroline hydrochloride are dissolved in 35 ml dist water. The solution is made up to 50 mL with dist. water. Apparatus and glass wares: magnetic stirrer magnetic stirring bar stirring bar remover crystallizing dish 115 · 65 4 beakers 100 mL beaker 50 mL measuring cylinder 100 mL Hazards and safety precautions: Potassium bromate is a strong oxidizer - contact with combustible materials may cause fire. Harmful if swallowed. Possible human carcinogen. Eye, skin and respiratory irritant. Conc. sulfuric acid is highly toxic. Causes severe burns. Malonic acid is harmful if swallowed, inhaled or absorbed through the skin. High concentrations are very destructive of mucous membranes. Safety goggles and protective gloves must be worn. Effective ventilation! Experimental procedure: Four solutions are prepared: Solution A: 6.75 g of KBrO3 in 80 mL of dist. water Solution B: 15.6 g of malonic acid in 100 mL of dist. water Solution C: 1.3 g of KBr in 70 mL of dist. water Solution D: 14 mL of conc. H2SO4 in of 65 mL dist. water. The mixture is allowed to cool to room temperature. The four solutions are poured into a crystallizing dish containing 400 mL of dist. water while stirring on a magnetic stirrer. After the yellow-brown color (bromine) has disappeared, 2 mL of ferroin solution are added to the mixture. Result: Ferroin-indicator added creates a red color. After approximately 75 seconds the color of the solution turns to a blue, that will disappear after a short time and a red color will appear again. Thus the color oscillates between red and blue. Video clip (Download RealPlayer .rm Datei) Discussion: Rubin R. Aliev: Belousov-Zhabotinsky-Reaction - Scheme of the elementary processes Reference: Demonstration Experiment on Video Briggs-Rauscher Oscillating Reaction Index of Lecture Experiments Search Lab Chemicals & Reagents Acids, Bases, Solvents, Stains. Since 1951 - Ships Same Day! www.rmreagents.com PCS Pipette Calibration Automated system for rapid, on-site traceable pipette calibration www.artel-usa.com Laboratory Automation Liquid Handlers, Robotic Pipettors, & Integrated Laboratory Solutions! www.BeckmanCoulter.com Demonstration Experiment on Video Briggs-Rauscher Reaction Objective: Mechanism of an Oscillating Reaction Peter Keusch Chemicals: hydrogenperoxide 30 % potassium iodate malonic acid manganese(II) sulfate monohydrate conc. H2SO4 starch, soluble German version Apparatus and glass magnetic stirrer wares: 4 magnetic stirring bars stirring bar remover crystallizing dish 140 · 75 3 beakers 1500 mL 3 beakers 500 mL beaker 150 mL 10 mL measuring pipette (fully graduated 0.1 mL divisions) pipette bulb measuring cylinder 500 mL 3 measuring cylinders 250 mL Cabinets Fixtures Hazards and safety precautions: Hoods Labs Stainless Epoxy Iodine is produced. Iodine is toxic - may be fatal if swallowed or Trespa Free AutoCAD Drawings! inhaled. Harmful by inhalation and through skin absorption. Readily www.milesco.net absorbed through skin. Very destructive of mucous membranes and upper respiratory tract, eyes and skin. Severe irritant. Conc. sulfuric acid is highly toxic. Causes severe burns. May be Hamilton Pipettes fatal if swallowed. May cause cancer through inhalation. Very Highest quantity with destructive of mucous membranes. least effort Complete control & accuracy. Potassium iodate is harmful if swallowed. May be harmful www.MicronicNA.com by inhalation or through skin absorption. Irritant. Corning Lab Hydrogenperoxide 30 % is toxic, corrosive - can cause Supplies serious burns. Eye contact can cause serious injury, possibly Beakers/Flasks/Funnels blindness. Harmful by inhalation, ingestion and skin contact. All Corning Products 800*967*5316 Safety goggles and protective gloves must be worn. The experiment www.BCScientific.com should be performed in a well ventilated room. Laboratory Supplies Save 10-25% on our Experimental procedure: most popular Laboratory Products! www.labdepotinc.com The following solutions are prepared in advance: Solution A: 410 mL of 30% hydrogenperoxide are diluted to 1.0 liter with * Graduated distilled water in a 1500 mL beaker. Cylinders * Solution B: 43 g of potassium iodate are dissolved in about 800 mL of dist. Superior quality water + 4.3 ml of conc. sulfuric acid in a 1500 mL beaker. The mixture is plastic. Safely and made up to 1000 mL with dist. water accurately measure Solution C: 16 g of malonic acid and 3.4 g of manganese (II) sulfate liquids. www.globescientific.com monohydrate are dissolved in about 500 mL of dist. water in a 1500 mL beaker. 3 g of soluble starch are dissolved in 100 mL of boiling dist. water in a 150 mL beaker. The starch solution is poured into the solution of malonic acid and manganese sulfate. The mixture is diluted with dist.water to 1000 mL. 250 mL of each the solutions A and B are poured into a crystallizing dish. The mixture is stirred vigorously with a magnetic stirrer.
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