# 8.1 Simple rate equations; orders of reaction; rate constants

a) explain and use the term rate of reaction

b) explain qualitatively, in terms of collisions, the effect of concentration changes on the rate of a reaction

c) explain and use the terms rate equation, order of reaction, rate constant, half-life of a reaction, rate-determining step

d) construct and use rate equations of the form rate = k[A]m[B]n (for which m and n are 0, 1 or 2), including:

(i) deducing the order of a reaction, or the rate equation for a reaction, from concentration-time graphs or from experimental data relating to the initial rates method and half-life method

(ii) interpreting experimental data in graphical form, including concentration-time and rate-concentration graphs

(iii) calculating an initial rate using concentration data (integrated forms of rate equations are not required)

e) (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

f) calculate the numerical value of a rate constant, for example by using the initial rates or half-life method

g) for a multi-step reaction:

(i) suggest a reaction mechanism that is consistent with the rate equation and the equation for the overall reaction

(ii) predict the order that would result from a given reaction mechanism (and vice versa)

h) devise a suitable experimental technique for studying the rate of a reaction, from given information

# 8.2 Effect of temperature on reaction rates and rate constants; the concept of activation energy

a) explain and use the term activation energy, including reference to the Boltzmann distribution

b) explain qualitatively, in terms both of the Boltzmann distribution and of collision frequency, the effect of temperature change on the rate of a reaction

c) explain qualitatively the effect of temperature change on a rate constant and hence the rate of a reaction

# 8.3 Homogeneous and heterogeneous catalysts including enzymes

a) explain and use the term catalysis

b) explain that catalysts can be homogenous or heterogeneous

c) (i) explain that, in the presence of a catalyst, a reaction has a different mechanism, i.e. one of lower activation energy

(ii) interpret this catalytic effect in terms of the Boltzmann distribution

d) describe enzymes as biological catalysts (proteins) which may have specificity

e) outline the different characteristics and modes of action of homogeneous, heterogeneous and enzyme catalysts, including:

(i) the Haber process

(ii) the catalytic removal of oxides of nitrogen from the exhaust gases of car engines

(iii) the catalytic role of atmospheric oxides of nitrogen in the oxidation of atmospheric sulfur dioxide (see also Section 13.1(f))

(iv) the catalytic role of Fe2+ or Fe3+ in the I–/S2O8(2–)

(v) the catalytic role of enzymes (including the explanation of specificity using a simple lock and key model but excluding inhibition)