3.1.5 Kinetics

Question 1

What is rate of reaction?

Answer 1

Rate of reaction is the change in the amount of reactant or product over time

Question 2

What does collision theory state

Answer 2

Reaction won’t take place between two particles unless the conditions are correct

Question 3

What are the conditions in collision theory which allow reactions to take place (direction)?

Answer 3

Particles need to collide in the right direction (facing each other the right way)

Question 4

What are the conditions in collision theory which allow reactions to take place (energy)?

Answer 4

Particles need to collide with at least a certain minimum amount of kinetic energy (activation energy)

Question 5

Define activation energy

Answer 5

minimum amount of kinetic energy particles need to react

Question 6

What is activation energy needed for?

Answer 6

this much energy is needed to break the bonds within reactant particles to start the reaction

Question 7

How easily do reactions with low activation energies happen

Answer 7

Reactions with low activation energies often happen easily

Question 8

How easily do reactions with high activation energies happen

Answer 8

Reactions with high activation energies don’t happen easily

Question 9

Why does a Maxwell Boltzmann graph start at (0,0)

Answer 9

Because no molecules have zero energy

Question 10

What does the peak of the curve on a Maxwell Boltzmann graph represent

Answer 10

Peak of the curve represents the most probable energy (Emp) of any single molecule

Question 11

What does just right of the peak of a Maxwell Boltzmann graph show?

Answer 11

Mean average energy of all the molecules is a bit to the right of the peak

Question 12

What does the area under a Maxwell Boltzmann distribution curve show

Answer 12

Area under a Maxwell Boltzmann distribution curve is equal to the total number of of molecules

Question 13

How does temperature affect rate of reaction?

Answer 13

Increasing the temperature, increases rate of reaction

Question 14

What happens to the proportion of molecules with at least the activation energy when temperature is increased

Answer 14

Greater proportion of molecules will have at least the activation energy and be able to react

Question 15

What happens when you increase temperature in terms of energy

Answer 15

If you increase temperature, the molecules will on average have more kinetic energy and will move faster

Question 16

What happens to molecules due to their increase in kinetic energy after a temperature increase

Answer 16

The molecules will be moving around quicker so they will collide more often

Question 17

How will increasing temperature affect the shape of the Maxwell Boltzmann distribution curve?

Answer 17

Increasing temperature will push the Maxwell Boltzmann distribution curve over to the right

Question 18

How will decreasing temperature affect the shape of the Maxwell Boltzmann distribution curve?

Answer 18

Decreasing temperature will the push the Maxwell Boltzmann distribution curve over to the left

Question 19

Does changing temperature change the area under the Maxwell Boltzmann distribution curve?

Answer 19

No as number of molecules stays the same

Question 20

Does changing temperature change the activation energy

Answer 20

Changing temperature doesn’t change the activation energy

Question 21

How does increasing temperature affect the most probable energy

Answer 21

Increasing temperature increases the most probable energy

Question 22

How does decreasing temperature affect the most probable energy

Answer 22

Decreasing temperature will decrease the most probable energy

Question 23

How does concentration affect rate of reaction

Answer 23

Increasing concentration will increase rate of reaction

Question 24

What does increasing concentration do to how close particles are together

Answer 24

If you increase the concentration of reactants in a solution, the particles will on average be closer together

Question 25

What happens as a result of particles being closer together

Answer 25

If particles are closer together, collisions are more frequent

Question 26

What happens if collisions are more frequent

Answer 26

If collisions are more frequent, there will be more chances for particles to react so rate of reaction increases

Question 27

How does changing concentration affect activation energy value

Answer 27

Changing concentration doesn’t change activation energy value

Question 28

How does changing concentration affect most probable energy value

Answer 28

Changing concentration doesn’t change most probable energy value

Question 29

How does increasing concentration affect area under the Maxwell Boltzmann distribution curve?

Answer 29

Increasing concentration increase area under Maxwell Boltzmann distribution curve If concentration is doubled, so will the area

Question 30

How does decreasing concentration affect area under Maxwell Boltzmann distribution curve

Answer 30

Decreasing concentration decreases area under Maxwell Boltzmann distribution curve If concentration is halved, so will the area

Question 31

How does increasing concentration affect the number of molecules with energies above activation energy

Answer 31

Increasing concentration increases molecules available to collide in a given volume. Will also be more molecules with energies above the activation energy

Question 32

How does increasing temperature affect the number of molecules that have at least the activation energy

Answer 32

At higher temperatures, more molecules have at least the activation energy

Question 33

How does changes in pressure affect rate of reaction

Answer 33

Changes in pressure affect rate of reaction the same way as changes in concentration

Question 34

What can you use catalysts to do?

Answer 34

You can use catalysts to make chemical reactions happen faster

Question 35

What does a catalyst do to rate of reaction

Answer 35

A catalyst increases the rate of a reaction

Question 36

How does a catalyst increase rate of reaction

Answer 36

Catalyst increases rate of reaction by providing an alternative reaction pathway with a lower activation energy

Question 37

Do catalysts get used up in reactions

Answer 37

Catalysts don’t get used up in the reaction

Question 38

Do catalysts take part in reactions

Answer 38

Catalysts do take part in reactions but are remade at the end of them

Question 39

Why does lowering activation energy increase rate if reaction

Answer 39

More particles with enough energy to react when they collide so in a set time more particles react

Question 40

Does adding a catalyst change the shape of the Maxwell Boltzmann distribution curve?

Answer 40

Maxwell Boltzmann distribution curve is unchanged as molecules still have the same amount of energy

Question 41

Does adding a catalyst change the activation energy

Answer 41

Adding a catalyst lowers the activation energy, so shifts it to the left on a Maxwell Boltzmann distribution curve

Question 42

How do you work out rate of reaction?

Answer 42

(Amount of reactant used or product formed) / (time)

Question 43

How does increasing pressure increase rate of reaction

Answer 43

Increasing pressure pushes all of the particles closer together so increases the number in a given volume, this increases the frequency of collisions and so also rate of reaction

Question 44

measuring rate of reaction practical: step 1

Answer 44

draw a black cross on a white tile and place a conical flask on top

Question 45

measuring rate of reaction practical: step 2

Answer 45

add the fixed volumes of sodium thiosulfate solution and HCl into the conical flask, measure initial temp and start stopwatch

Question 46

measuring rate of reaction practical: step 3

Answer 46

wait until cross disappears (precipitate forms) and stop the stopwatch, noting down the time. Record temp of solution

Question 47

measuring rate of reaction practical: step 4

Answer 47

calculate average temperature using the initial and final temperatures

Question 48

measuring rate of reaction practical: step 5

Answer 48

repeat practical at different temperatures, as temp increases so should rate of reaction

Question 50

how does surface area affect rate of reaction

Answer 50

increasing surface area increases rate of reaction

Question 51

how does increasing surface area increase rate of reaction

Answer 51

more particles are exposed to the other reactant there is a greater chance of particles colliding, which leads to more successful collisions per second the rate of reaction increases