Kinetics

Question 1

N2O5 –> 2NO2 +1/2O2 (show how pressure changes)

Answer 1

Show how pressure changes

Question 2

aA+bB --> cC+dD 
Integrated rate law assuming:
- 1st order
- 2nd order
- 3rd order

Answer 2

fun

Question 3

Find half life of 1st, 2nd and 3rd order reactions

Answer 3

YAY

Question 4

Why is a transition state a pre-equilibria?

Answer 4

It can go on to form the product or fall back to the reactant

Question 5

Show that A –> B is not simply first order?

Answer 5

ha

Question 6

What is the steady-state approximation?

Answer 6

states the reactive intermediate is formed slowly but reacts quickly

Question 7

What are the assumptions for Lindemann theory? and show how lindemann shows that a first order rxn can become second order at a low pressure

Answer 7

• molecule A is excited by the collision with another A
• excited molecule reacts quickly
• excited molecule needs a certain amount of energy before reacting
• Excited molecule can be dexcited

Question 8

Explain Arrhenius in relation to collision theory?

Answer 8

• molecules must collide with energy greater than or equal to the activation energy for a rxn reaction to occur (only energy of initial approach are used to overcome Eac)
• rate proportional to encounter rate (A) x Eac
• However, A is often smaller than calculated from kinetic theory, meaning a steric factor (P) was bolted on
• Where P=1 when all collisions cause a reaction
• collision theory only applies to gases

Question 9

Explain activated complex theory?

Answer 9

• if two reactants meet and have Eac, they form an activated complex with loosened bonds
• steric factor is an integral part of the theory
• applies to gases and solutions
• applies to elementary reactions/steps
• K2 = KbT/h

Question 10

Show how activated complex theory can calculate A for the Arrhenius equation (eyring equation)

Answer 10

YAYAY

Question 11

How can you tell whether a reaction follows Arrhenius?

Answer 11

• separate and ln arrhenius
• compare to y=mx+c and plot
• if straight line = Arrhenius

Question 12

What are the four different steps of a radical reaction?

Answer 12

initiation, propagation, termination and inhibition

Question 13

Within activated complex theory, what does KbT/h and e^(s/R) show?

Answer 13

KbT/h = attempt at the activation barrier per second
e^(s/R) = steric factor

Question 14

What does KbT/h and e^(s/R) represent?

Answer 14

KbT/h = attempts to overcome Eac per second
e^(s/R) = Steric Factor