Photo credit: Tim Ellis
Reaction Kinetics, also commonly known as Chemical Kinetics, is easily voted as one of the most difficult Physical Chemistry topics in JC1 (or J1) curriculum under the Singapore’s GCE A-Level H2 Chemistry syllabus (code 9729). The others will be Chemical Energetics and Chemical Equilibrium.
Every year, we always hear from new students who joins our JC2 (or J2) H2 Chemistry Tuition Classes that they dislikes Reaction Kinetics and don’t really know what is happening in their JC lectures and tutorials when it comes to this topic. Many of them would request from us to conduct topical intensive revision workshops to help them to revise and master this important topic.
One of the main reason i found out was that IP or A-Level students tend to study Reaction Kinetics in the wrong way. They went to memorise all the content they can find in their school lecture notes and expect to do well in the upcoming examinations by regurgitating. To master Reaction Kinetics, students would need to truly understand the underlying concepts and apply it to different scenarios in exam-based questions.
Did i also mention that Reaction Kinetics are commonly tested in GCE A-Level H2 Chemistry Practicals? Time to pay attention to this very important topic!
Let’s start by asking ourselves some guiding questions with regards to this topic:
- What do we mean by rate of reaction?
- What are the factors affecting rate? How does each factor affect rate?
- How can we determine and express the relationship between rate and concentration mathematically? How are the other factors affecting rate featured in this mathematical equation?
- What is half-life and how is it connected to the different orders of reaction?
- What is rate constant and how does it affects the overall rate of reaction?
- What can we infer about the mechanism of a reaction from the order of reaction?
- Why do most chemical reactions not occur in a single step?
- What are the general types of catalysts? How are they similar and how do they differ in their mode of action?
- Do you know that enzymes are biological catalysts? Do you know how they work?
Since this topic is so important, why not we take a closer look at the learning outcomes as stipulated by the Singapore Examination & Assessment Board (SEAB)?
Based on GCE A-Level H2 Chemistry syllabus (code 9729), students must be able to:
(a) explain and use the terms: rate of reaction; rate equation; order of reaction; rate constant; half-life of a reaction; rate-determining step; activation energy; catalysis
(b) construct and use rate equations of the form rate = k[A]m[B]n (limited to simple cases of single-step reactions and of multi-step processes with a rate-determining step, for which m and n are 0, 1 or 2), including:
(i) deducing the order of a reaction by the initial rates method
(ii) justifying, for zero- and first-order reactions, the order of reaction from concentration-time graphs
(iii) verifying that a suggested reaction mechanism is consistent with the observed kinetics
(iv) predicting the order that would result from a given reaction mechanism
(v) calculating an initial rate using concentration data
(c)(i) show understanding that the half-life of a first-order reaction is independent of concentration
(ii) use the half-life of a first-order reaction in calculations
(d) calculate a rate constant using the initial rates method
(e) devise a suitable experimental technique for studying the rate of a reaction, from given information
(f) explain qualitatively, in terms of frequency of collisions, the effect of concentration changes on the rate of a reaction
(g) show understanding, including reference to the Boltzmann distribution, of what is meant by the term activation energy
(h) explain qualitatively, in terms both of the Boltzmann distribution and of collision frequency, the effect of temperature change on a rate constant (and hence, on the rate) of a reaction
(i) (i) explain that, in the presence of a catalyst, a reaction has a different mechanism, i.e. one of lower activation energy, giving a larger rate constant
(ii) interpret this catalytic effect on a rate constant in terms of the Boltzmann distribution
(j) outline the different modes of action of homogeneous and heterogeneous catalysis, including:
(i) the Haber process (CASE STUDY)
(ii) the catalytic removal of oxides of nitrogen in the exhaust gases from car engines (CASE STUDY)
(iii) the catalytic role of atmospheric oxides of nitrogen in the oxidation of atmospheric sulfur dioxide (CASE STUDY)
(iv) catalytic role of Fe2+ in the I–/S2O82– reaction (CASE STUDY)
(k) describe enzymes as biological catalysts which may have specific activity
(l) explain the relationship between substrate concentration and the rate of an enzyme-catalysed reaction in biochemical systems
I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends.
Do stay tuned to the upcoming posts as i will be discussing the concepts in Reaction Kinetics in more details.
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PPS: If you need help with your A-Level H2 Chemistry, do join us in our weekly A-Level H2 Chemistry Tuition Class.
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- 4 Steps to Solve Redox Reactions in JC A-Level H2 Chemistry
- Key Definitions & Formulae in Atoms, Molecules and Stoichiometry
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