CHAP. 9: CHEMICAL KINETICS [CONTENTS] 271
9.2 Simple reactions systematics
We will assume that a reaction starts at timeτ= 0. The initial concentration of the substances
involved in the reaction will be denoted using the subscript 0 , e.g.cA0,cB0,... In reactions with
two or more reactants, we will deal only with those cases in which the partial orders are natural
numbers. These cases are most frequent in practice. For the sake of simplicity we will mostly
leave the right side of chemical reactions unspecified (i.e. we will write “products”).
9.2.1 Zero-order reaction
9.2.1.1 Type of reaction
A→products. (9.16)9.2.1.2 Kinetic equation
−
dcA
dτ=k. (9.17)9.2.1.3 Integrated form of the kinetic equation.
For time as a function of the reactant concentration we have
kτ=cA0−cA where cA0≥cA≥ 0. (9.18)For the concentration of substance A as a function of time we have
cA=cA0−kτ, where τ≤cA0
k. (9.19)
9.2.1.4 Reaction half-life
τ 1 / 2 =cA0
2 k. (9.20)
A zero-order reaction ends at time
τ=
cA0
k, (9.21)
when the concentration of the reactant falls to zero.