NJC 7 Kinetics H1 (Notes)

National Junior College SH1 H1 Chemistry REACTION KINETICS Content ● Simple rate equations; orders of reaction; rate constants ● Concept of activation energy ● Effect of concentration, temperature, and catalysts on reaction rate ● Heterogeneous catalysis ● Enzymes as biological catalysts Learning Outcomes Candidates should be able to: (a) explain and use the terms: rate of reaction; rate equation; order of reaction; rate constant; half-life of a reaction; 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, 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 conc-time graphs (iii) calculating an initial rate using concentration data (c) show understanding that the half-life of a first-order reaction is independent of concentration (d) explain qualitatively, in terms of frequency of collisions, the effect of concentration changes on the rate of a reaction (e) show understanding, including reference to the Boltz mann distribution, of what is meant by the term activation energy (f) 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 (g) (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 in terms of the Boltzmann distribution (h) outline the mode of action of heterogeneous catalysis, as exemplified by the catalytic removal of oxides of nitrogen in the exhaust gases from car engines (i) describe enzymes as biological catalysts which may have specific activity © 2022 National Junior College All Rights Reserved. No part of this publication may be produced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording or any other information storage and retrieval system, without prior permission in writing from the copyright owner.

National Junior College SH1 H1 Chemistry 2 1 BASIC CONCEPT IN KINETICS 1.1 COLLISION THEORY (Understanding reaction at particulate level) For a reaction between two particles to occur two conditions must be met: 1) The particles must collide in the correct orientation. 2) The particles must collide with sufficient minimum energy (known as the activation energy) to bring about the necessary re -organisation of the bonds in the colliding particles. Assuming product to be , When particles collide at the correct orientation and sufficient energy , this collisio