C6 - Chemical Reaction

Question 1

What is a successful collision? [2]

Answer 1

Particles must collide with enough energy for a chemical reaction to happen.

Question 2

What is activation energy? [2]

Answer 2

Minimum amount of energy needed for a reaction to happen

Question 3

What is the symbol for activation energy? [1]

Answer 3

Ea

Question 4

What is the rate of reaction? [2]

Answer 4

• How fast the reaction goes
• How often there are successful collisions

Question 5

What two things does the rate of reaction depend on? [2]

Answer 5

• the frequency of collisions
• the energy of the collision

Question 6

What things (factors) affect the rate of reaction? [5]

Answer 6

1. concentration
2. surface area
3. temperature
4. pressure
5. catalysts

Question 7

What is a catalyst? [2]

Answer 7

Increases the rate of reaction and is unchanged at the end of a reaction

Question 8

What are practical ways to investigate the rate of reaction? [3]

Answer 8

• change in mass of reactant
• change in mass of product
• formation of a gas

Question 9

How is the rate of reaction increased if there’s a larger number of particles or if there’s an increase in pressure? [1]

Answer 9

more collisions

Question 10

How is the rate of reaction increased if the surface area is increased? [1]

Answer 10

more space for a reaction

Question 11

How is the rate of reaction increased if the temperature is increased? [1]

Answer 11

particles have more kinetic energy

Question 12

How is the rate of reaction increased if there’s a catalyst? [1]

Answer 12

provides an alternate route to products from reactants (lower activation energy)

Question 13

Do the reactants or the products have more energy? [1]

Answer 13

products

Question 14

Where is the activation energy always between? [2]

Answer 14

reactants and the peak

Question 15

Where is the overall energy change always between? [2]

Answer 15

reactants and products

Question 16

What do reactants need to make products? [1]

Answer 16

additional energy from around them

Question 17

What is an exothermic reaction? [3]

Answer 17

It transfers thermal energy to the surroundings leading to an increase in the temperature of the surroundings

Question 18

What is an endothermic reaction? [3]

Answer 18

It takes in thermal energy from the surroundings leading to a decrease in the temperature of the surroundings

Question 19

What is the transfer of thermal energy during a reaction called? [1]

Answer 19

enthalpy change, ΔH, of the reaction

Question 20

What is ΔH like for exothermic reactions? [1]

Answer 20

negative

Question 21

What is ΔH like for endothermic reactions? [1]

Answer 21

positive

Question 22

What is ΔH? [1]

Answer 22

overall energy change of the reaction

Question 23

Which reactions are exothermic? [2]

Answer 23

• neutralisation
• displacement

Question 24

Which reactions can be endothermic? [2]

Answer 24

• salt dissolving
• precipitation

Question 25

Why is there a negative sign in exothermic reactions? [3]

Answer 25

- exothermic reactions give out energy to their surroundings - temperature rise - negative sign shows that energy is given out

Question 26

Why is there a positive sign in endothermic reactions? [3]

Answer 26

- endothermic reactions take in energy from their surroundings - temperature drop - positive sign shows that energy is taken in

Question 27

How do you know if a reaction if endo or exothermic in terms of bond breaking and bond making? [4]

Answer 27

- if the energy taken in to break bonds is GREATER than the energy released in making bonds = ENDOTHERMIC - if the energy taken in to break bonds is LESS than the energy released in making bonds = EXOTHERMIC

Question 28

What should you measure to find the rate of reaction, in general? [2]

Answer 28

1. amount of reactant used up per unit of time 2. amount of product made per unit of time

Question 29

How does the speed of the rate of reaction affect the curve on a graph? [2]

Answer 29

- the faster the rate of reaction = STEEPER curve - the slower the rate of reaction = SHALLOWER curve

Question 30

In exothermic reactions do the reactants have more or less energy than the products? [1]

Answer 30

more

Question 31

In endothermic reactions do the reactants have more or less energy than the products? [1]

Answer 31

less

Question 32

Between which two points does bond breaking occur? [1]

Answer 32

reactants and peak

Question 33

Between which two points does bond making occur? [1]

Answer 33

peak and products

Question 34

Between which two points is energy released or taken in? [1]

Answer 34

reactants and products