kinetics_fall2011_preclass_3per_page[1]

kinetics_fall2011_preclass_3per_page[1] - 9/21/11 1 Chapter...

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Unformatted text preview: 9/21/11 1 Chapter 16: Kinetics 16.1: Factors that influence reaction rate 16.2: Expressing the reaction rate 16.3: The rate law and its components 16.4: Integrated rate laws: Concentration changes over time 16.5: The effect of temperature on reaction rate 16.6: Explaining the effects of concentration and temperature 16.7: Reaction Mechanisms: Steps in the overall reaction 16.8: Catalysis: Speeding up a chemical reaction Half-life is defined as the time required for one-half of the initial quantity (or concentration) of reactant to be consumed. Drug Half-life Caffeine 5 hours Cocaine 45 minutes Valium 18 hours Morphine 3 hours Nicotine 2 hours Streptomycin 5 hours Salicylic Acid* 2~15 hours *Doses of 300 to 650 mg have a half-life of 3.1 to 3.2 hours; with doses of 1 gram, the half-life is increased to 5 hours and with 2 grams it is increased to about 9 hours. Hydrogen Peroxide Hydrogen Peroxide is an unstable chemical substance producing nascent oxygen, which is essential in most H 2 O 2 applications. As it is mainly used as a bleaching agent, the oxidant, paper & pulp, and dyeing & processing industries are the biggest consumers of hydrogen peroxide. Its non-toxic properties are expected to reduce environmental pollution. Pure hydrogen peroxide solution is stable with weak decomposition. However, when it comes in contact with heavy metals or various organic compounds, or mixes with impurities, it produces oxygen gas and decomposition heat. http://eng.dcchem.co.kr/product/p_basic/p_basic14.htm 9/21/11 2 Time-dependence of concentration during the iodide- catalyzed decomposition of hydrogen peroxide Time, s [H 2 O 2 (aq)], M [O 2 (g)], M 0 0.882 0.000 60 0.697 0.0925 120 0.566 0.158 240 0.372 0.255 360 0.236 0.323 480 0.152 0.365 600 0.094 0.394 2 H 2 O 2 (aq) 2 H 2 O(l) + O 2 (g) I- (aq) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 100 200 300 400 500 600 Time /sec Concentration /M 2 H 2 O 2 (aq) 2 H 2 O(l) + O 2 (g) I- (aq) Time-dependence of concentration during the iodide- catalyzed decomposition of hydrogen peroxide Rate of reaction can be defined as rate of disappearance of a reactant or rate of appearance of a product. 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 100 200 300 400 500 600 Time /sec Concentration /M Rate of reaction = - [H 2 O 2 ] t 2 H 2 O 2 (aq) 2 H 2 O(l) + O 2 (g) Rate of reaction = [O 2 ] t 9/21/11 3 For this reaction, the rate changes as the reaction proceeds (as [H 2 O 2 ] changes) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 100 200 300 400 500 600 Time /sec Concentration /M 2 H 2 O 2 (aq) 2 H 2 O(l) + O 2 (g) The rate law, not the rate of reaction, is usually reported Rate of Reaction = - [H 2 O 2 ] t = k [H 2 O 2 (aq)] a k and a are determined experimentally (the influence of products on reaction rates are often ignored) k is the specific rate constant a is the order of the reaction (here, with respect to H 2 O 2 ) 2 H 2 O 2 (aq) 2 H 2 O(l) + O 2 (g) How is concentration as a function of time data used to determine the rate law for the...
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kinetics_fall2011_preclass_3per_page[1] - 9/21/11 1 Chapter...

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