Chemistry 1301A/B Lecture Notes - Lecture 26: Collision Theory, Reaction Rate, Activation Energy

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31 Aug 2017

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Kinetics is the study of the rate of a chemical reaction. The major topics covered in this half-unit are: factors that affect the rate of reaction, rate law, reaction mechanisms. A rate is change per unit time; a chemical reaction rate is generally expressed as a change in the amount of concentration of some reactant or product per unit time (mol/l s). There are several factors which affect the rates of chemical reactions: the nature of the reactants, concentration and surface area, temperature, catalysts, the nature of the reactants. Collision theory states that for a reaction to occur, the reacting particles must: collide with each other, moreover they must collide with sufficient energy (activation energy, ea, the correct orientation/geometry. A heterogeneous reaction is one in which the reactants are in different states and the reaction occurs at the surface or interface where the two states meet.

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I need help getting the chemical equations in part 4

Factors Affecting the Rates of Chemical Reactions 25-5 4. The Influence of Temperature the test tube with the evolved gas. The gas coming (a) Measure 5 mL of solution A (used in part over first wl contain some air that was present in into a test tube. Measure 4 mL of water and mL flask. After 2-3 min, test the gas in the Erlen of 3% H2O2 into a second test tube. Place both test meyer flask by inserting a glowing splint into the tubes in a 250-mL beaker of warm water (50Â°C). flask. Does the gas support combustion? what is the After about 3 min H202 solution into a 50-mL beaker, stir, and note the time. When the blue color appears, note and only the H202 solution to the flask. Continuously record the elapsed time. Compare the reacton swirl the contents of the flask. Does the gas evolve time with that observed for the second reaction more slowly? After a few minutes' wait, you should be mixture you studied in part 1 pou r solution A and then the identity of the gas? Rinse the flask and repeat the experiment, adding able to tell whether the CuCl2 catalyzes the reaction. Now fill another test tube with water and place it (b) Ignition Temperature. Review the Safety Pre over the gas delivery tube. Remove the stopper just cautions. In a fume hood, place 10 to 20 drops of methanol in a 30-mL beaker. Remove the beaker to your lab bench. Heat the end of a glass stirring rod at the tip of the inner blue cone of a Bunsen burner until the glass starts to soften. Quickly drop of 3 M CuCl, and 1 drop of 3 M FeCl, in that touch the heated end to the methanol. A chemical reaction should begin; if it does not, reheat the swirl the solution in the flask, and record the time rod and try again. Stay at arm length from the required to fill a 13 x 100 mm test tube with gas. beaker Do not touch the beaker until it has cooled long enough to add 2 drops of 3 M FeCl. Insert the stopper and continuously swirl the solution. Note and Rinse the flask. Add to it 20 mL of 3% H2O2, 1 order. Quickly replace the stopper, continuously record the time required to fill the test tube with gas Repeat the procedure using 20 mL of 3% H2O2 Describe the reaction that takes place. Write a ba5 anced chemical equation for the reaction. Why doesn't methanol burst into flames at room tem- drops of 3 M CuC, and 5 drops of 3 M FeC Quickly stopper the flask and continuously swirl the contents of the flask. Note and record the time required to fill a 13 Ã 100 mm test tube with gas. exposed to air? (c) Obtain a small square of cotton cloth (muslin) and a book of matches. (The cotton cloth should be tightly woven, about 2 to 3 cm on a side, and cleanly cut, so there are no ragged edges.) Work- ing in a hood, place about 10 mL of 50:50 (vv) 2-propanol-water in a 50- or 100-m beaker. Using crucible tongs, grasp the square by one corner and dip it into the 2 propanol-water solu tion. Lift the cloth and allow the excess solution to drain until no more solution drips off the cot ton-Place a small watch glass over the solution in the beaker. Carry the cotton, still held in the tongs, to your lab bench. Have a lab partner light a match and bring it just near enough to the square of cotton (held in the tongs) to ignite the 2 propanol-soaked cotton. Make certain that no other person is within arm's length of the flaming cloth. When the flame dies out, carefully note the condition of the cloth. How can the 2-propanol 6. The Importance of Mixing Reactants (a) Half-fill two 13 Ã 100 mm test tubes with water. Drop a small crystal of solid KMno, into each tube. Put one tube aside in a test tube rack or beaker and let it remain undisturbed. Swirl the second tube to dissolve the crystal of KMnO Observe the crystal in the undisturbed tube every few minutes, noting how long it takes for the crystal to dissolve and then to spread (diffuse. Record your observations. (b) Add 10 mL of 0.50 M H2C204 (oxalic acid) to 10 mL of 6 M H2S04 and mix thoroughly. Place 8 mL of this solution into each of two 15 x 125 mm test tubes. Measure out two separate 8 ml por tions of 0.005 M KMno. Add one portion of KMno, solution to one of the test tubes contain- ing oxalic acid, holding the test tube at a 45 angle and carefully pouring the KMnO, down the side of the test tube to avoid mixing the two solu- tions. Note the time. Pour another 8 mL of KMno4 into the second test tube, stopper the tube, mix by inverting the tube several times, and note the time. As the reactions proceed, Mno will oxi- dize the oxalic acid to CO, and will itself be reduced to colorless Mn2+ ion. Record the times required for the solutions in the two test tubes to become completely colorless burn without igniting the cotton? S. Effect of Catalysts on the Rate of Decomposi- tion of HOz Using the same apparatus as in part 3a, place 20 mL of 3% H2O2 in the flask. Fill a 13 Ã 100 mm test tube with water and invert it over the gas delivery tube. Then add 20 drops of 3 M CuCh to the flask, replace the stopper, continuously swirl the contents, and note and record how long it takes to fill

Chemistry 1301A/B Lecture Notes - Lecture 26: Collision Theory, Reaction Rate, Activation Energy

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