Module 3 Chapter 10

Question 1

What is rate of reaction

Answer 1

A measure of how quickly a reaction occurs.

Question 2

What are the three ways to calculate rate of reaction

Answer 2

Rate of reaction = mass of product produced / time
Rate of reaction = mass of reactant used / time
Reaction rate = change in concentration / time

Question 3

What is the graph of concentration against time for the products and reactants of a reaction

Answer 3

DRAW IT

Question 4

What does this graph show us

Answer 4

That the initial rate of reaction is the highest.
Reaction rate decreases the longer the reaction goes.
When 1 of the reactants run out there will be no further reaction.

Question 5

What are the 5 ways that rate of reaction can be changed

Answer 5

Concentration of reactants
The temperature
Surface area
Pressure (for gases)
Catalysts

Question 6

What are the three factors needed for a successful collision/ reaction

Answer 6

The particles need to have sufficient energy (activation energy)
The particles have to collide
The particles should be in the correct orientation

Question 7

What is the effect of increasing concentration of reactants on rate of reaction and why

Answer 7

Increasing the concentration of solution will increase the rate of reaction. As there are more reactant particles in a given volume, allowing for a higher frequency of collisions and therefore successful collisions.

Question 8

What has the same effect as increasing the concentration of the reactants

Answer 8

Increasing the pressure for gases

Question 9

What is the effect of decreasing concentration of reactants on rate of reaction and why

Answer 9

Decreasing the concentration of solution will decrease the rate of reaction. As there are less reactant particles in a given volume, resulting in a lower frequency of collisions and therefore successful collisions.

Question 10

What is the effect of increasing the temperature of the reactants on the rate of reaction

Answer 10

If you increase the temperature of the reactants a higher proportion of the reactants have the activation energy or more this results in an increase in the frequency of successful collisions resulting in an increased rate of reaction. An increase in temperature also means that the reactants have a greater kinetic energy leading to an increase in the frequency of collisions and successful collisions resulting in a greater rate of reaction.

Question 11

What is the effect of decereasing the temperature of the reactants on the rate of reaction

Answer 11

If you decrease the temperature of the reactants a lower proportion of the reactants have the activation energy or more this results in a decrease in the frequency of successful collisions resulting in a decreased rate of reaction. A decrease in temperature also means that the reactants have a lower kinetic energy leading to an decrease in the frequency of collisions and successful collisions resulting in a lower rate of reaction.

Question 12

What is the impact of increasing the surface area to volume ratio on rate of reaction

Answer 12

If you increase the surface area to volume ratio more reactant particles are available for collision, collisions are more likely, leading to a greater frequency of collisions and therefore an increase in rate of reaction.

Question 13

What is the impact of decreasing SA:VOL ratio on rate of reaction

Answer 13

If you decrease the surface area to volume ratio less reactant particles are available for collision, collisions are less likely, leading to a lower frequency of collisions and therefore an decreased in rate of reaction.

Question 14

What is the effect of catalysts on rate of reaction

Answer 14

Catalyst increase the rate of chemical reactions, by lowering the activation energy providing another reaction pathway. So a greater proportion of the particles have the activation energy or more resulting in a greater rate of reaction.

Question 15

What happens during a chemical reaction

Answer 15

New product formed
Fizzing/ effervescence / gas given off
Colour change

Question 16

How can these changes be used to measure rate of reaction

Answer 16

Measure the volume of gas produced in a given time using a gas syringe or upturned cylinder.
Measure the change in mass over time.
Measure how long it takes for a cross to disappear.

Question 17

At what time is the initial rate of reaction measured

Answer 17

It is measured at t = 0

Question 18

How are instantaneous rates of reaction measured

Answer 18

A tangent to the curve at that time is drawn and then using the tangent a gradient is calculated to work out rate of reaction.

Question 19

What is a catalyst

Answer 19

A substance that changes the rate of a chemical reaction without undergoing any permanent change itself.

Question 20

What is a feature of a catalyst

Answer 20

They are not used up during a reaction

Question 21

What may catalyst do

Answer 21

They may react with a reactant to form an intermediate ( a species formed during a reaction that reacts further and is not present in the final products) or may provide a surface on which the reaction can take place.

Question 22

What happens to catalysts at the end of a reaction

Answer 22

They are regenerated

Question 23

What are the two types of catalyst

Answer 23

Homogenous catalysts : is in the same physical state as the reactants it reacts with
Heterogenous catalyst : is in a different physical state to the reactants it reacts with

Question 24

When catalysts provide a surface for the reaction to take place on what are the order of events and there names

Answer 24

Adsorption - weakly bonded onto the surface of catalyst
Reaction
Desorption - after reaction product molecules are released

Question 25

What are some examples of catalyst in real life

Answer 25

Platinum and palladium catalyst are used in catalytic converted of cars where harmful gases are turned into harmless gases.
Enzymes are biological catalysts.

Question 26

What are enzymes

Answer 26

Large protein molecules that are specific to a substrate and a reaction. There active site is keyed to that molecule.

Question 27

What are enzymes important for

Answer 27

Pharmaceutical development

Question 28

How can enzymes be effected by PH and temperature

Answer 28

DRAW THE GRAPHS

Question 29

What happens past the conditions that an enzyme is meant to work out

Answer 29

The enzyme can denature

Question 30

What is autocatalysis

Answer 30

The process by which the product of a reaction acts as a catalyst for the reaction itself.

Question 31

What are the benefits of using a catalyst

Answer 31

Activation energy lowered, which means less energy is needed in the reaction to take place
Therefore lower temperatures can be used which saves money and resources
More profit and less harmful effects of energy generation

Question 32

Draw a Boltzman’s distribution curve

Question 33

What is assumed in a Boltzmann’s distribution

Answer 33

All collisions between particles and the surface of the container are elastic
(a collision in which there is no loss of kinetic energy in the systems as a result of the collision)

Question 34

Draw a Boltzmans’ distribution with an increase in temperature

Question 35

What does the area under the curve represent

Answer 35

The total number of molecules

Question 36

Therefore when temperature increases what has to stay the same and what does it cause the curves to do

Answer 36

The area has to remain the same.
So the peak gets lower as the curve shifts to the right.

Question 37

Draw a Boltzman’s distribution for a lower temperatures

Question 38

Draw a Boltzman’s distribution for the presence of a catalyst

Question 39

Why does the Boltzman’s distribution height decrease and curve shift to the right when temperature increases

Answer 39

More molecules have an energy that is greater than the activation energy. Therefore the curve has shifted to the right, however, the height of the curve decreases as the number of molecules stays the same which is represented by the area under the curve.

Question 40

Why does the activation energy shift to the left in the presence of a catalyst in the Boltzman’s distribution curve.

Answer 40

A catalyst provides an alternative reaction route with a lower activation energy. As a result the activation energy shifts to the left and a higher proportion of the particles have the activation energy required or more.