reaction rates

Question 1

What does rate of chemical reaction measure

Answer 1

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

Question 2

Rate of reaction equation

Answer 2

change in concentration / time

Amount of reactant used or product made / time

Question 3

Why is rate of reaction fastest in the beginning

Answer 3

each reactant is at its highest concentration

Question 4

Factors that change rate of reaction

Answer 4

Temp
Catalyst
surface area
concentration

Question 5

What does collision theory state

Answer 5

for reaction to occur
particles must collide
particles must have sufficient energy - kinetic energy
Particles must collide with the correct orientation

Question 6

How is enthalpy change measured in a graph

Answer 6

products to reactants

Question 7

How can you show effect of SA to the rate of reaction

Answer 7

reacting marble chips with acid. The carbon dioxide gas evolved can be collected and its volume measured over time. Repeat with marble chips of different size

Question 8

Effect of temperature on rate

Answer 8

higher total no of collisions means higher no of successful collisions
Higher activation energy, higher proportion of collisions successful

Question 9

Activation energy meaning

Answer 9

The minimum energy needed for a chemical reaction to happen

Question 10

Where is the activation energy in an energy profile

Answer 10

Between reactants and top of the profile

Question 11

What does a Maxwell-Boltzmann Distribution show

Answer 11

The energy in gas particles

Question 12

Do particles of a gas in sample move at the same speed

Answer 12

Move at a different speed

Have a different amount of kinetic energy

Question 13

What does the highest peak of the Maxwell-Boltzmann Distribution mean

Answer 13

The most likely energy of a particle in a sample

Question 14

What does the line to the right of the highest peak mean

Answer 14

The mean energy particles have

Question 15

What does the area under the graph mean

Answer 15

Total number of molecules

Question 16

How does increasing pressure increase rate

Answer 16

Particles are closer together - collide more often
More frequent collisions
Higher chance of collision

Question 17

How does increasing concentration increase rate

Answer 17

Particles are closer together

Question 18

What is a catalyst

Answer 18

Substance that increases the rate of reaction by providing an alternative pathway that has lower activation energy. Chemically unchanged. More molecules exceed activation energy

Question 19

What are the 2 types of catalysts

Answer 19

Homogeneous and Heterogeneous

Question 20

Heterogeneous catalyst

Answer 20

Different state to the reactants

Question 21

Homogeneous catalyst and what they form

Answer 21

Same state as the reactants
Forms intermediate species by reactants combining with the reactants to form the products.
Catalyst is reformed again

Question 22

4 reasons catalysts are used in the industry

Answer 22

Lower temp - less co2 produced
Speed up a reaction by providing an alternative pathway
Change the property of a product
Reduce the use of toxic reactants

Question 23

Example of a reversible reaction

Answer 23

Haber process
making ammonia
NH3

Question 24

Characteristic of an equilibrium system

Answer 24

Rate of forward reaction = rate of backward reaction
The concentration of product or reactant do not change
In a closed system

Question 25

What does le chateliers principle state

Answer 25

When there is an external change to a system in equilibrium, the reaction tries to minimise the change

Question 26

What does an increase in the concentration of reactants lead the equilibrium system to do and in what situation?

Answer 26

Shifts to the opposite direction

Only works in homogenous equilibria (same state)

Question 27

what happens if we increase the pressure in equilibria

Answer 27

shifts to the side with fewest moles and vice versa

Question 28

What happens if we increase the temp in equilibria

Answer 28

Shifts to the endothermic side vice versa

Question 29

What does a catalyst do to the equilibria

Answer 29

No effect on the position - has no effect on the yeild

speed up the rate of reaction equally

Question 30

What is the pressure, temperature, catalyst for making ethanol?

Answer 30

60 atmospheres
300 degrees
phosphoric acid

Question 31

How does lowering the temperature to make ethanol lead to a compromise?

Answer 31

Equilibrium shifts to the right
However, lower temp means lower rate of reaction.
300 degrees is a compromise between yield and rate

Question 32

How does increasing the pressure to make ethanol lead to a compromise?

Answer 32

High pressure would increase the rate and shift to the right

But are expensive because thicker pipes are needed.

Question 33

What does Kc tell you

Answer 33

Calculate equilibrium constants

Indicates whether there are more products or equilibrium in the system