Kinetics Lecture 2

Question 0

How are the orders determined experimentally?

Answer 0

We deliberately change the concentrations of each reactant in turn and see how this affects the rate of reaction

Question 1

What is the method of initial rates?

Answer 1

Measuring the change in concentration of a reactant or product with time in the initial stages of the reaction.

Question 2

How do we find x?

Answer 2

Measure initial rates for different values of [A]o while holding [B]o constant

Question 3

How do we find y?

Answer 3

Measure initial rates for different values of [B]o while holding [A]o constant

Question 4

Why measure initial rates?

Answer 4

It is a convenient way to determine the rate

Question 5

How do we determine the rate constant from the initial rate?

Answer 5

Rearrange the rate law and plug in one set of experimental data

Question 6

What does the integrated rate law for 1st order reactions do?

Answer 6

A version of the rate law that relates concentration to time

Question 7

What does a plot of ln[A]t vs t give?

Answer 7

A straight line

• slope = -k
• y intercept = ln[A]o

Question 8

How can you show that a reaction is 1st order?

Answer 8

• show that a plot of ln[A] vs t is linear

- can obtain k from slope of plot

Question 9

What is the half life?

Answer 9

The time taken for the reactant concentration to reach half its initial value

Question 10

For a first order reaction what is important about t1/2?

Answer 10

The value of t1/2 is independent of the initial concentration of A

Question 11

What are examples of first order reactions in relation to half life?

Answer 11

• decay of radioactive isotopes

- decay of pesticides in the environment