Kinetics

Question 1

Collision theory (2)

Answer 1

Reactions can only occur when collisions take place with enough activation energy
They must also collide at the correct orientations for a reaction

Question 2

Define activation energy

Answer 2

The minimum energy at which particles need to start to reaction and break the relevant reactant bonds

Question 3

what does the Maxwell Boltzman distribution show?

Answer 3

The distribution shows the spread of energy that molecules are gas or liquid have a particular temperature.

Question 4

what is on the axes of the Maxwell Boltzmann distribution?

Answer 4

Number of molecules with this energy on y axis
Energy on x axis

Question 5

Why does the distribution curve go through the origin?

Answer 5

there are no molecules with no energy

Question 6

Where is the mean on the maxwell boltzmann distribution curve?

Answer 6

To the right of the peak, which is the Emp - most probable energy

Question 7

Why do some molecules have low energy on the MB Distribution?

Answer 7

Some collisions cause some particles to slow down

Question 8

What does the area under the MB Distribution curve represent?

Answer 8

The total number of particles present

Question 9

What to remember about drawing the end of the MB distribution?

Answer 9

Never let energy distribution meet the x axis aside from the origin as there is no maximum energy for molecules

Question 10

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

Answer 10

particles gain energy through collisions

Question 11

As temperature increases, what does the MB distribution shift towards?

Answer 11

towards having more molecules with higher energies

Question 12

what happens when the temperature is increased in the MB distribution?

Answer 12

at higher temperatures both the Emp and mean energy shift to higher energy values, although the number of molecules with those energies decrease

more molecules have the activation energy or greater

Question 13

define rate of reaction

Answer 13

The rate of reaction is defined as a change in concentration of a reactant or product in a unit time

Question 14

how do you find the rate of reaction from a graph with concentration of reactant on the Y axis and its time on the X axis? what about initial rate?

Answer 14

find a gradient of the curve by drawing a tangent
at the start of the reaction

Question 15

what are the effects of increasing concentration/pressure on rate?

Answer 15

there are more the number of particles per unit volume, so the particles collide with the greater frequency, and there will be a higher frequency of effective collisions

Question 16

what are the effects of increasing concentration/pressure on the MB distribution curve?

Answer 16

The shape of the energy distribution curve does not change
The curves will overall be higher and the area under the curve will be greater because there are more particles

Question 17

does increasing concentration/pressure have an effect on the proportion of particles with energy higher than activation energy?

Answer 17

No

Question 18

in rates curves, what do different volumes of the same initial concentrations have in common?

Answer 18

The same initial rate and initial gradient, provided everything else is the same

Question 19

what is the effect of increasing temperature on the MB distribution curve?

Answer 19

as temperature increases a significantly bigger proportion of particles have an energy greater than Ea on the graph, so the frequency of successful collisions increases

Question 20

what is the effect of increasing surface area on a reaction’s rate?

Answer 20

successful collisions will occur more frequently between the reaction particles, and this increases rate of reaction

Question 21

Define catalyst

Answer 21

The substance that increases its reaction right without being used up in the reaction by providing an alternate route, with a lower activation energy

Question 22

how does a catalyst increase rate of reaction?

Answer 22

as the Ea is now lower more particles have an energy that’s greater than Ea so there will be a higher frequency of effective collisions