Data graphs for rate 2 no2 2 no o2 lnp no2 vs time 48

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Unformatted text preview: n. overall Reaction Mechanism Reaction The following mechanism is proposed for a reaction: NO2(g) + NO2(g) → NO(g) + NO3(g) NO3(g) + CO(g) → NO2(g) + CO2(g) NO2(g) + CO(g) → NO(g) + CO2(g) Overall Intermediate – forms in one step of the reaction but disappears in Intermediate a following step. following Catalyst – is used up (a reactant) in one step but forms as a Catalyst product in the later step. product Reaction Mechanisms Reaction Proposed mechanisms must satisfy the experimental Proposed rate law expression. rate Usually the rate law is related to the rate-determining Usually step in the reaction; the slow step in the reaction. step Rate-determining step – the step that controls the Rate-determining speed of the reaction. speed Reaction Mechanisms Reaction For the reaction discussed before For NO2(g) + CO(g) → NO(g) + CO2(g) The experimental rate law is found to be: rate = k[NO2]2 rate The proposed mechanism was: NO2(g) + NO2(g) → NO(g) + NO3(g) NO3(g) + CO(g) → NO2(g) + CO2(g) Overall Slow step Reaction Mechanisms Reaction The reactants in the slow step are present The in the rate law. in Any proposed mechanism must agree with Any the rate law. the Reaction Mechanism Reaction For the overall reaction: For 2 N2O5 4 NO2 + O2 The following mechanism is proposed: N2O5 N2O4 + O O + N2O5 N2O4 + O2 What is a possible next step in the reaction? What The intermediate in the reaction is: A) N2O5 b. N2O4 c) O d) O2 Activation Energy Activation Activation Energy (Ea): The potential energy barrier that must be overcome before reactants can be converted into products. products. ΔH Temperature Dependence of k Temperature As the temperature increases what happens to the As rate of the reaction? rate E a − RT k = Ae A – Arrhenius constant, freq. of collisions with correct Arrhenius orientation. orientation. T – temp in Kelvin R – Ideal Gas Constant in Joules (8.314 J/K-mol) The Arrhenius Equation The A simpler way to use this is by comparing the rate constant at just simpler two temperatures: two Ea 1 1 k2 ln =− − k1 R 2 T1 T If the rate of a reaction doubles by increasing the temperature by If 10°C from 298.2 K to 308.2 K, what is the activation energy of the 10 from reaction? reaction? Energy Profile of Catalyzed Reaction Energy polar stratospheric clouds contain ice crystals that catalyze reactions that release Cl from atmospheric chemicals Catalytic Hydrogenation Catalytic H2C=CH2 + H2 → CH3CH3...
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