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C. Y. Yeung (CHW, 2009)

Maxwell-Boltzmann Distribution & Collision Theory. Maxwell-Boltzmann Distribution & Collision Theory. p.01. Interpretation of Rate of Gaseous Rxn at Molecular Level. C. Y. Yeung (CHW, 2009). Conc. / Pressure. Surface Area. Temperature. Catalyst. 1. Molecules with K.E.  E a , and

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C. Y. Yeung (CHW, 2009)

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  1. Maxwell-Boltzmann Distribution&Collision Theory Maxwell-Boltzmann Distribution&Collision Theory p.01 Interpretation of Rate of Gaseous Rxn at Molecular Level C. Y. Yeung (CHW, 2009)

  2. Conc. / Pressure Surface Area Temperature Catalyst 1. Molecules with K.E.  Ea, and 2. Collide in right orientation. p.02 Factorsaffecting the Rate of Rxn …? Rxn occurs via a pathway with a lower Ea Frequency of Collisions  Kinetic energy of particles  Areas of Contact  No. of Collisions  No. of Effective Collisions Rate of Rxn  Effective Collisions Collision Theory

  3. Frequency of Collisions  Conc. / Pressure Molecules have different Kinetic Energy (K.E.) p.03 Frequencyof Collisions is Important ! i.e. Distribution of K.E. of molecules in a system During collisions, some molecules gain energy from the others, and some molecules loss energy to the others.

  4. Molecules with “most probable speed” Distribution of K.E. at temperature = T1 No. of molecules with K.E.  Ea rxn occurs! Area under curve  total no. of molecules p.04 In the system, molecules have a range of K.E. Maxwell-Boltzmann Distribution

  5. no. of molecules p.05 Distribution of K.E. atDifferent Temperature? Temp., more molecules take part in rxn.  rate of rxn . Ea Areas under curve 00C, 250C and 1000C are the same! (no. of molecules in system remains constatnt)

  6. p.06 Explain how temp. affects the Rate of Rxn … Temp.  Collision Frequency  Energy transfer between molecules becomes more frequent. Wider distribution of K.E. No. of molecules have K.E.  Ea  No. of molecules take part in rxn  Rate of Rxn 

  7. p.07 p. 77 Q.4 (1996 --- M-B Distribution) As temp. , fraction of molecules with high K.E. . Hence, force exerted by the collision of molecules on the container wall .

  8. p.08 p. 78 Q.7(b) (1998 --- M-B Distribution) As a higher temp., the portion towards high K.E. is much larger. More molecules would have sufficient energy to overcome Ea and to react. Increasing the number of effective reactant increases the rate of reaction.

  9. p.09 Catalyst & M-B Distribution: Catalyst provides an alternative pathway for the reaction to occur. Positive Catalyst provides a pathway with lower Ea. Ea’ (catalysed) Ea (uncatalysed)

  10. p.10 Conclusion 5 factors affecting the rate of reactions (with explanations in terms of frequency of effective collisions. [Collision Theory] Maxwell-Boltzmann Distribution of Molecular Speeds and Kinetic Energy Explain how temperature change and use of catalyst affect the rate of reaction with Maxwell-Boltzmann Distribution

  11. p.11 Next …. Single / Multi-stage Reaction & Energy Profile, Catalyst (p. 58-69)

  12. p.12 Assignment Pre-lab: Expt. 9 Determination of Activation Energy [due date: 26/2(Thur)] p. 53 Check point 15-1 p. 58 Check point 15-2 [due date: 26/2(Thur)]

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