CH 232 Chapter 13 Notes

Chemistry Chapter 13 Chemical Kinetics
Sec 13.1: Catching Lizards: Pages 597 and 598

Sec 13.2: The Rate of a Chemical Reaction:
Chemical Reaction: H2 + I2  2HI
H
H
[¿¿ 2]t 1
[¿ ¿ 2]t 2− − Δ[ I 2 ] +1 Δ [ HI]
Rate of Reaction: t 2−t 1 Or Or (respect to the
Δt 2 Δt
¿
−Δ [H 2]
=−¿
Δt
product)
*Note: The reaction rate is defined as the negative of the change in concentration of
the reactant per change in time because the reactant concentrations decrease (the
change in the concentration is negative). Since the product concentration increases as
the reaction proceeds, the change in concentration of a product is positive.

General Definition for Reaction Rate:
aA + bB  cC + dD

−1 Δ[ A ] −1 Δ [B] +1 Δ[C ] +1 Δ[ D]
Rate = = = =
a Δt b Δt c Δt d Δt

Sec 13.3: The Rate Law: The Effect of Concentration on Reaction Rate:
Rate Law-the relationship between the rate of the reaction and the concentration of
the reactants
A  Products
Rate = k[A]n
k= constant of proportionality (rate constant)
n=the reaction order which determines how the rate depends on the concentration of
the reactant

If n=0, reaction is zero order (rate is independent of concentration of A)
If n=1, reaction is first order (rate is directly proportional to concentration of A)
If n=2, reaction I second order (rate is proportional to the squared concentration A)

Reaction Order for Multiple Reactants:
aA + bB  cC + dD
Rate = k[A]m[B]n
m = reaction order with respect to A
n = reaction order with respect to B

Overall Order- the sum of the exponents (m+n)

, Sec 13.4: The Integrated Rate Law: The dependence of Concentration on Time:

Integrand Rate Law-a relationship between the concentrations of the reactants and
time for a chemical reaction


A  Products
First-Order Integrated Rate Law:
Rate = k[A]
− Δ[ A]
*Note: Since Rate = we can write:
Δt
− Δ[ A]
Rate = = k [A]
Δt
[ A ]t
Ln[A]t = -kt + ln[A]0 or ln =−¿ kt
[ A ]0
[A]t = concentration of A at anytime
[A]0 = initial concentration of A


Second-Order Integrated Rate Law:
Rate = k[A]2
− Δ[ A]
*Note: Since Rate = we can write:
Δt
− Δ[ A]
Rate = = k [A]2
Δt
1 1
=kt +
[ A ]t [A]0
[A]t = concentration of A at anytime
[A]0 = initial concentration of A

Zero-Order Integrated Rate Law:
Rate = k[A]0 = k
− Δ[ A]
*Note: Since Rate = we can write:
Δt
− Δ[ A]
Rate = =k
Δt
[A]t = -kt + [A]0
[A]t = concentration of A at anytime
[A]0 = initial concentration of A

Half Life (t1/2)- the time required for the concentration of a reactant to fall one-half of
its initial value

First Order Reaction Half Life: