CHEM 102 Lab- Exp 24 - prelab solution PDF

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Experiment 24 Pre-Lab Answers (A rate law and activation energy)

1. Not found 2.a For the kinetic study on the reaction of iodide ions with hydrogen peroxide the 'START TIME' should be the time of addition of hydrogen peroxide into the mixture of KI solution, sodium thiosulfate solution, starch and deionized water, in acidic medium. And the 'STOP TIME' should be the exact time when the blue color just appears.

2.b The color of the solution at STOP TIME will be blue.

2. c During the kinetic study, when hydrogen peroxide is added to the potassium iodide solution in acidic medium, the hydrogen peroxide oxidizes the iodide ions to iodine, according to the following equation: H2O2 + 2I- + 2H+ = I2+ 2H2O At the end point, the blue color appears due to the presence of starch, which forms an intense dark blue colored complex with very small amounts of triiodide anions (I3- forms in the presence of both iodine and iodide in the solution).

3.a The deionized water is devoid of any impurities or other ions, which can cause interference in the kinetic study and hence it is used in the kinetic study.

3.b Acetic acid-sodium acetate buffer solution is used in the kinetic study to maintain the pH of the solution within the range 3 – 6.

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5.B...