Kinetics

Question 1

Define activation energy

Answer 1

The minimum energy which particles need to collide to start a reaction

Question 2

What is needed for a reaction to take place

Answer 2

When collisions take place between particles having sufficient energy

Question 3

What does the maxwell boltsmann distribution curve show

Answer 3

The spread of energies that
molecules of a gas or liquid have at a particular temperature

Question 4

How can a reaction go to completion if few particles have energy greater than EA?

Answer 4

Particles can gain energy through collisions

Question 5

Define rate of reaction

Answer 5

The rate of reaction is defined as the change in concentration of a substance in unit time.
The usual unit is mol dm-3s-1

Question 6

Describe the effect of increasing conc and pressure on the rate of the reaction

Answer 6

More particles per unit volume and so the particles collide with a greater frequency and there will be a higher frequency of effective collisions

Question 7

How does the MB curve change with a change in concentration/ pressure

Answer 7

Shape of the curve does not change ( the peak is at the same energy) so the emp and the mean energy do not change
Curve will be higher and the area under the curve will be greater
This means more molecules will have energy greater than the activation energy

Question 8

Describe the effect of temperature on the rate of reaction

Answer 8

At higher temperatures the energy of the particles
increases. The particles collide more frequently and more often with energy greater than the activation energy.
More collisions result in a reaction.

Question 9

Describe the effect of increasing the temperature on the MB curve

Answer 9

As the temperature increases, the graph shows that a significantly bigger proportion of particles have energy greater than the activation energy, so the frequency of successful collisions increases.

Question 10

Describe the effect of increasing the surface area on the rate of reaction

Answer 10

Increasing surface area will cause successful collisions to occur more frequently between the reactant particles and this increases the rate of the reaction

Question 11

Describe the role of a catalyst

Answer 11

Catalysts increase reaction rates without getting used up
They do this by providing an alternative route with a lower
activation energy

Question 12

Describe the effect of adding a catalyst on the maxwell boltzmann distribution curve

Answer 12

The activation energy will be marked lower on the distribution curve meaning more particles have energy which is greater than or equal to the Ea
This means there is more frequent and sucessful collisions