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CHEMICAL KINETICS CHEMICAL KINETICS The applications of chemistry mainly focus on chemical reactions. ►Need to know several of its characteristics:  Stoichiometry  Energetics  Rate CHEMICAL KINETICS The area of chemistry that concerns reaction rates is called chemical kinetics < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> The Rate Law Versus the Stoichiometry of a Reaction CH3Br (aq) + OH-(aq) → CH3OH(aq) + Br -(aq) Rate = k(CH3Br)(OH-) (CH3)3CBr(aq) +OH-(aq) → (CH3)3COH(aq) + Br-(aq) Rate = k((CH3)3CBr) ► The rate law for a reaction cannot be predicted from the stoichiometry of the reaction; it must be determined experimentally. The Rate Law Versus the Stoichiometry of a Reaction 2 HI(g) → H2(g) + I2(g) Rate = k(HI)2 2 N2O5(g) → 4 NO2(g) + O2(g) Rate = k(N2O5) < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> Order of Molecularity One step reaction: ClNO2(g) + NO(g) → NO2(g) + ClNO(g) Other reactions occur by a series of individual steps: Step 1: N2O5 NO2 + NO3 Step 2: NO2 + NO3 Step 3: NO + NO3 NO2 + NO + O2 2 NO2 SINGLE STEP REACTION CH3Br(aq) + OH-(aq) → CH3OH(aq) + Br-(aq) Rate = k(CH3Br)(OH-) REACTION MECHANISM (CH3)3CBr(aq)+OH-(aq)→(CH3)3COH(aq)+ Br-(aq) (CH3)3CBr → (CH3)3C+ + Br(CH3)3C+ + H2O → (CH3)3COH2+ Slow step Fast Step (CH3)3COH2+ + OH- → (CH3)3COH + H2O Fast step Rate = k[(CH3)3CBr] < TARGET="display"> < TARGET="display"> < TARGET="display"> HETEROGENEOUS CATALYST Hydrogenation of olefine CH2=CH2 (g) + H2 (g) → CH3-CH3 HETEROGENEOUS CATALYST V2O5 SO2 (g) + ½ O2 (g) → SO3 (g) HOMOGENEOUS CATALYST Troposphere: NO catalyst NO (g) + ½ O2(g) → NO2 (g) NO2 (g) → NO (g) + O (g) O (g) + O2 (g) → O3 (g) HOMOGENEOUS CATALYST Stratosphere: NO catalyst NO (g) + O3 (g) → NO2 (g) + O2 (g) NO2 (g) + O (g) → NO (g) + O2(g) O (g) + O3 (g) → 2O2 (g) < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display"> < TARGET="display">