A4 kinetics 1

Question 1

rate of chemical reaction def

Answer 1

measure of how fast a reactant is being used up or how fast a product is formed

Question 2

alternating rate of chemical reaction factors

Answer 2

conc/ pressure

temp

catalyst

surface area of solid reactants

Question 3

Describe how increasing concentration affects rate

Answer 3

1- Increases rate

2- More particles per unit volume

3- More frequent collisions

4- More successful collisions per unit time

Question 4

Describe how increasing pressure affects rate

Answer 4

1- Increases rate of reaction

2- more molecules per unit volume

3- Increases the concentration of molecules

4- collision frequency is higher

5- More successful collisions per unit time

Question 5

Describe how increasing temperature affects rate

Answer 5

1- Increases rate

2- Particles have more kinetic energy

3- More particles have energy greater than the activation energy

4- More successful collisions per unit time

Question 6

higer solid SA increases rates because

Answer 6

1- more of solid is exposed to other particles

2- so collision frequency is higher

3- so there are more successful collisions per unit time

Question 7

Define a catalyst

Answer 7

1- Lowers activation energy of reaction

2- By providing an alternative route for the reaction

3- Meaning a greater proportion molecules have energy that’s exceeds than the activation energy

Question 8

Describe the difference between homogenous and heterogenous catalysts

Answer 8

1- Homogenous catalysts are in the same physical state as the reactants

2- Heterogenous catalysts are in a different physical state to the reactants

Question 9

When is it difficult to classify if a catalyst is homogenous or heterogenous

Answer 9

When the reactants have different physical states

Question 10

Describe and explain the importance of catalysts

Answer 10

1- Allow reactions to occur at lower temperatures

2- Reduce energy demand from combustion of fossil fuels

3- Less CO2 produced

Question 11

Describe and show how a catalyst affects a Maxwell-Boltzmann distribution graph

Answer 11

1- Greater area under the curve with energy above the activation energy

2- A greater number of molecules have energy greater than the activation energy

3- A greater proportion of molecules have more energy greater than
activation energy

Question 12

Draw a Maxwell-Boltzmann graph, and show and explain how an increased temperature would affect this

Answer 12

1- greater area under the curve with energy above the activation energy

2- A greater number of molecules have energy greater than the activation energy

3- more particles have at least the activation so they have enough ernegy to collide and react

Question 13

boltsmzan distribution effect of catlalyst reaction

Answer 13

activation energy shifts to left

Question 14

Describe the apparatus and method to investigate rate with volume

Answer 14

1. Weigh excess metal using mass balance
2. Measure volume of acid using measuring cylinder

3.Mix metal and acid in conical flask

4. Measure gas volumes from gas syringe at regular intervals

Example: 15s using stopwatch

5. Continue until no further change in volume

Question 15

Describe the apparatus and method to investigate rate with mass

Answer 15

1- Weigh excess mass of metal using mass balance

2- Measure volume of acid with measuring cylinder

3- Mix metal and acid in conical flask

4- Measure initial mass

5- Re-weigh at regular time intervals
Example: 15s using stopwatch

6- Continue until no further change in mass

Question 16

rate equation

Answer 16

change in conc/ time

Question 17

rates units

Answer 17

mol dm -3 s-1

Question 18

tangent

Answer 18

gradient rise/ run

finds rate of reaction

Question 19

Describe a method to calculate initial rate

Answer 19

Plot a XXX against time graph

Draw a tangent at t=0s

Gradient of tangent = XXX/Time

Gradient of tangent = initial rate

Question 20

collision theory

Answer 20

reacting particles must collide for a reaction to occur

Question 21

collisions to be effective

Answer 21

1- particles collide with correct orientation

2- Particles have sufficient energy to overcome the activation energy barriers of the reaction

Question 22

rate of reaction explained

Answer 22

rate of reaction decreases

conc decreases as reactants used up

less frequent colllisions

Question 23

rate of reaction decreases over time why? explain in terms of collision theory

Answer 23

conc decreases

fewer collisions per second

less frequent collisions

Question 24

using mass(balance) vs volume (gas syringe) method adv and dis

Answer 24

adv–> no loss of gas

dis–> small loss in mass