Rates of Chemical Reactions Ii

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Rates of Chemical Reaction II
Pre-Lab Summary:
First we will set up the experiment as shown in Figure 2, and then we will fill the trough with room temperature water and record the temperature and we will also add the room temperature water to the buret until it is about 10ml from the top. If there are no leaks in the apparatus, we will add 10ml of KI to 15ml of distilled water in a 125ml flask. We will swirl the flask so that it achieves room temperature, then we will add 5ml of H2O2 and quickly stopper the flask. While one student continues to swirl the flask, the other should observe the volume of oxygen produced, after 2ml of gas has been evolved. The recordings should be written down at 2ml intervals until 14ml of oxygen has been evolved. Next, we will repeat the experiment (making sure everything is the same, including the temperature of the bath water) by adding 10ml of KI and 10ml of H2O2 (after swirling the flask), then quickly stoppering the flask and measuring the readings. This will all be repeated again for a third time by adding 20ml of KI and 5ml of distilled water, swirling and then adding 5ml of H2O2. Next, we will adjust the bath temperature so that it is 10 degrees C to 12 degrees C higher and repeat the first part of the last experiment but continue the readings until there is no more oxygen evolving. Next, we will pour 1ml of the ending mixture in a small test tube and add 10 drops of Pb(NO3)2 and mix and observe. Then we will dilute it to .2ml of KI with about 5ml of distilled water and then add 10 drops of Pb(NO3)2 and record observations.

Questions:
1. How does the rater of formation of O2 compare with (a) the rate of formation of H2O and (b) the rate of disappearance of H2O2 for reaction [4]? a. Half
b. Half
2. Why should the levels of water in the leveling bulb and buret be kept the same? c. So that the same pressure is on all liquids
3. Why were you instructed to keep swirling the Erlenmeyer flask?...
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