Rates And Energy

Question 0

What equation is used for rate?

Answer 0

How much product is made / time

Question 1

What is rate?

Answer 1

A measure of how much product is used up or the amount of product formed.

Question 2

What energy type releases energy to the surroundings?

Answer 2

Exothermic

Question 3

What energy is absorbed from the surroundings?

Answer 3

Endothermic

Question 4

What energy type is most common?

Answer 4

90% exothermic

10% endothermic

Question 5

Example of exothermic reaction?

Answer 5

Combustion & respiration

Question 6

Example of endothermic reaction?

Answer 6

Thermal decomposition

Question 7

2 properties of a catalyst?

Answer 7

• is not used up or changed

- lowers the activation energy in a reaction

Question 8

Why are catalysts used

Answer 8

• speed up the rate of a chemical reaction
• use less energy because of that
• costs are reduced because of that
• reactions are therefore more efficient

Question 9

Can you always use the same catalyst?

Answer 9

No you use different catalysts for different reactions

Question 10

Examples of materials commonly used as catalysts? What do they have in common?

Answer 10

Transition metals:
Titanium
Gold
Silver
Nickel

Question 11

What are the problem with using those materials to catalyse a reaction?

Answer 11

They are toxic and produce waste

Question 12

What is an alternative material being used to catalyse reactions?

Answer 12

Enzymes

Question 13

What factors affect how quickly a reaction happens?

Answer 13

Catalysts
Surface area
Temperature
Light intensity
Pressure
Concentration

Question 14

What is the definition of activation energy?

Answer 14

The minimum amount of energy needed to start a reaction

Question 15

What is the collision theory?

Answer 15

The theory that particles must collide to react and have the correct activation energy

Question 16

Explain why increasing the temperature increases the rate of reaction?

Answer 16

• the particles move faster becauE they have more kinetic energy
• collisions between particles are more frequent/ greater chance of collisions
• more particles have the correct activation energy
• the rate of reaction increases

Question 17

What does increasing the pressure/ concentration do in a reaction?

Answer 17

It increases the frequency of collisions between particles and so increases the rate of reaction

Question 18

What does temperature affect/not affect?

Answer 18

It affects the speed of reaction

NOT Affects the amount of product

Question 19

What happens to a chemical recarion it the surface area of the solid increases?

Answer 19

The rate of reaction increases because there’s more surface area so an increased chance of collisions (frequency of collisions) between reacting particles

Question 20

Define a reversible reaction?

Answer 20

When the products can react together to form reactants

Question 21

What type of energy change has to occur in reversible reactions ?

Answer 21

Endothermic and exothermic

Question 22

What happens to energy in a reversible recarion ?

Answer 22

The amount of energy in the reaction stays the same

Question 23

What is energy measured in ?

Answer 23

Joules

Kilojoules

Question 24

If in an equation about energy change there is a - + What type of energy change is it?

Answer 24

- energy is released to the surroundings | + energy is absorbed from the surroundings

Question 25

When can Exothermic changes be used? Why?

Answer 25

- In hand warms, self heating cans | - exothermic reactions release energy into the surroundings generally as heat

Question 26

When can endothermic reactions be used? Why?

Answer 26

- ice packs - they absorb energy from the surroundings and as the energy is usually in the form of heat energy the temperature decreases

Question 27

What is the effect of increasing the pressure on the rate of reaction? 3

Answer 27

- the rate increases - because particles are more likely to collide/the particles are closer together - so frequency of collisions increases

Question 28

If the surface area is greater what happens to the rate of reaction?

Answer 28

The reaction is faster with a greater surface area

Question 29

If the surface area is smaller what happens to the rate of reaction?

Answer 29

The reaction is slower

Question 30

What is meant by activation energy?

Answer 30

The minimum amount of energy that are needed to start a reaction

Question 31

Other than a catalyst how could the 3student increase the rate of reaction?

Answer 31

Increase temperature Increase concentration Increase surface area

Question 32

Why does a metal have to be in molten for electrolysis?

Answer 32

So that the ions can move and carry charge

Question 33

What is the effect of increasing the pressure on the rate of reaction? 3

Answer 33

- the rate increases - because particles are more likely to collide/the particles are closer together - so frequency of collisions increases

Question 34

If the surface area is greater what happens to the rate of reaction?

Answer 34

The reaction is faster with a greater surface area

Question 35

If the surface area is smaller what happens to the rate of reaction?

Answer 35

The reaction is slower

Question 36

Other than a catalyst how could the 3student increase the rate of reaction?

Answer 36

Increase temperature Increase concentration Increase surface area

Question 37

How can you tell from a graph that the rate of reaction has increased?

Answer 37

Steeper line

Question 38

When do chemical reactions occur?

Answer 38

When the reacting particles collided with the right activation energy

Question 39

How can you make reactions more likely to happen?

Answer 39

Increase the chance of reacting particles colliding with each other Increasing the energy that they have when collision occurs

Question 40

Why does concentration increase the rate of reaction?

Answer 40

More particles of reactants in the same volume