An Exercise in Solution Preparation – The BR Oscillation Reaction
By Issra Mehdi
Date: January 28, 2010
This experiment was performed using familiarity with molarity, percent composition, and density to prepare solutions that will display chemical oscillation upon mixing. Solution A was prepared by transferring the calculated amount of malonic acid to a volumetric flask with a small amount of distilled water. Then the calculated amount of manganese sulphate solution was pipeted to the same volumetric flask along with distilled water to the mark. Solution A was then transferred to a labelled beaker. Solution B was prepared by collecting 30mL of sulfuric acid and the calculated amount of potassium iodate into a beaker. The solution was heated to a low setting until the potassium iodate was completely dissolved. After the solution cooled down, it was transferred into a volumetric flask and was made up to the volume with .080 M H2SO4. Solution C contained only one solute which was hydrogen peroxide. It was a reagent grade 30% (w/w) aqueous solution which required a dilution. Calculations were made and checked prior to preparing the solution. The solution was then diluted to the mark with distilled water. Solution D which was 3% starch solution was already prepared in a dropper bottle. Four drops of solution D was added into a clean beaker. 10 mL of solutions A, B, and C were transferred into separate graduated cylinders. The solutions were then poured into the beaker containing starch at the same time. After some mixing, my lab partner and I noticed a colour change appearing in our solution. The sequence of colours we observed went from clear yellow clear blue clear yellow. The reaction came to a complete stop when it turned black. Although the calculations were done properly and everything was set up like the way it was supposed to be, my lab partner and I ran through some problems as we were conducting this experiment. One source of error...
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