Unit 3 - Chemistry in Society

Question 1

What are industrial process designed to do?

Answer 1

Maximise profit

Minimise impact on environment

Question 2

What are the five factors affecting process design?

Answer 2

Availability, sustainability and cost of feedstocks
Opportunities for recycling
Energy requirements
Marketability of by-products
Product yield

Question 3

What is a raw material?

Answer 3

An organic/natural substance

Question 4

Give an example of a raw material.

Answer 4

Metal ores
Oxygen
Fossil fuels

Question 5

What is a feedstock?

Answer 5

What we can get from a raw material

Question 6

Give an example of a feedstock?

Answer 6

Iron

Crude Oil

Question 7

What is the formula to find mass in grams?

Answer 7

m = n x gfm

Question 8

What is the formula to find number of moles?

Answer 8

n = c x v

Question 9

How do you scale products and reactants?

Answer 9

Divide by original no, times by new number

Question 10

Why are percentage yields carried out?

Answer 10

To ensure the production is economically viable

Question 11

How do you calculate the percentage yield?

Answer 11

Balance
Scale
= Theoretical
% = Actual/Theoretical x 100

Question 12

How do you work out what is limiting and what is in excess?

Answer 12

Mole ratio
Find no of moles through double calculation = have
Refer to mole ratio to scale = need
Have __moles of __, need __moles therefore __is limiting and __ is in excess

Question 13

Why atom economy calculated?

Answer 13

To see how much of the reactants are converted into desired products

Question 14

How would you work out the atom economy of a reaction?

Answer 14

Write mole ratio
Find gfm of each compound and scale with its own ratio
%AE = mass of desired products/total mass of reactants x 100

Question 15

What are the four ways to control the rate of a reaction?

Answer 15

Temperature
Particle size/surface area
Concentration
Catalysts

Question 16

What is activation energy?

Answer 16

The minimum quantity of energy required to start a reaction

Question 17

What increases the rate of reaction?

Answer 17

Increased concentration
Increased temperature
Increased surface area/Decreased particle size
Use of a catalyst

Question 18

Why does increasing concentration increase the rate of reaction?

Answer 18

Increasing the concentration increase the number of reactant particles present, so more successful collisions will occur

Question 19

Why does increasing the temperature increase the rate of reaction?

Answer 19

Particles move faster and collide with more particles at a greater force, so the number of successful collisions increases

Question 20

In a graph, how is an increase of temperature shown in terms of activation energy?

Answer 20

Graph moves to the right and the peak becomes flatter/shorter

Question 21

In a graph, how is an decrease of temperature shown in terms of activation energy?

Answer 21

Graph moves to the left and the peak is higher

Question 22

How do catalysts increase the rate of reaction?

Answer 22

By lowering the activation energy

Question 23

How do you show the effect of a catalyst on a energy particle graph?

Answer 23

Move the activation energy line towards the y axis

Question 24

What are the two conditions for a successful collision to occur?

Answer 24

Correct collision geometry

Kinetic energy equal to or greater than the activation energy

Question 25

In terms of gases, how does pressure affect reaction rate?

Answer 25

Increased pressure = less space between particles = increased rate Decreased pressure = more space between particles = decreased rate

Question 26

How do you calculate the rate of reaction?

Answer 26

R = 1/t

Question 27

Given a graph, how do you find the activation energy of the forward reaction?

Answer 27

Reactants line to peak of curve

Question 28

Given a graph, how do you find the activation energy of the reverse reaction?

Answer 28

Products line to peak

Question 29

Given a graph, how do you find the enthalpy change of the forward reaction?

Answer 29

Reactants line to products line | If exothermic, will be negative

Question 30

Given a graph, how do you find the enthalpy change of the reverse reaction?

Answer 30

Products line to reactants line | If endothermic, will be negative

Question 31

Looking at a reaction pathway graph, how would you show the effect of a catalyst?

Answer 31

Line from reactants to products with a lower peak

Question 32

*Catalysts have no effect on the overall enthalpy change*

Question 33

What are the three stages of catalyst mechanism?

Answer 33

Adsorption Reaction Desorption

Question 34

What occurs during adsorption?

Answer 34

Reactants form temporary bond with active site of the catalyst Weakens bonds between molecules, lowers Activation energy

Question 35

What occurs during reaction in catalyst mechanism?

Answer 35

Molecules are fixed so the geometry is favourable for a successful collision. Molecules react on catalyst surface

Question 36

What occurs during desorption?

Answer 36

The product molecules leave the catalyst | The active site can be occupied again to restart the process

Question 37

What is the activated complex?

Answer 37

Unstable arrangement of atoms between reactants and products Fleeting existence Occurs at the peak of the reaction pathway graph

Question 38

What is the equation for volume?

Answer 38

V = n x MV

Question 39

How would you calculate the volume of a gas when given a mass of another substance?

Answer 39

``` Mole ratio Use gfm to find mass 1 mole Scale to given mass - gas should be the MV OORRR put given mass into n=m/gfm use mole ratio V= n x MV ```

Question 40

How do you work out the volume composition in a reaction?

Answer 40

``` Mole ratio Ignore any solids and liquids Sub in one known volume, scale up to other Compare with question ___cm3 of __ produced ___cm3 unreacted ___cm3 total ```

Question 41

What is the enthalpy of combustion?

Answer 41

The energy released when 1 mole of a substance is burned completely in oxygen

Question 42

How do you work out the enthalpy of combustion?

Answer 42

E = c x m x delta T | Scale up to one mole

Question 43

What measurements should be taken to calculate the enthalpy of combustion?

Answer 43

``` Start temperature of water End temperature of water Start mass of spirit burner End mass of spirit burner Volume of water ```

Question 44

Why might the worked value not match the data book value?

Answer 44

Incomplete combustion Evaporation of alcohol Heat energy lost to surroundings Reading Uncertainties

Question 45

What is Hess's Law?

Answer 45

The enthalpy change in converting reactants to products is the same regardless of the route by which the reaction takes place

Question 46

How do you write Hess's Law calculations?

Answer 46

Balance target equation Rewrite/flip equation to make provided equations match target Score through unneeded elements Write out target equation and the total enthalpy change

Question 47

How do you calculate the enthalpy change, by using bond enthalpies?

Answer 47

Divide page into two Breaking (endo)(+) = Making (exo)(-) = Sum

Question 48

At equilibrium, what are the rates of the forward and backwards reaction?

Answer 48

Equal

Question 49

When are the concentrations of products and reactants constant?

Answer 49

At equilibrium

Question 50

On a concentration graph, where does equilibrium occur?

Answer 50

When the two lines level off

Question 51

On a rate graph, where does equilibrium occur?

Answer 51

When the two lines meet

Question 52

What are the three ways to shift equilibrium?

Answer 52

Changing concentration Changing temperature Changing pressure

Question 53

*Catalysts do not have an effect on equilibrium*

Question 54

What effect does increased temperature have on equilibrium?

Answer 54

Favours endothermic reaction

Question 55

What effect does decreased temperature have on equilibrium?

Answer 55

Favours exothermic reaction

Question 56

What effect does increased pressure have on equilibrium?

Answer 56

Increased pressure = favours side of the smallest no of moles of gas

Question 57

What effect does decreased pressure have on equilibrium?

Answer 57

Decreased pressure = favours side with largest number of moles of gas

Question 58

What effect does an addition of a reactant have on equilibrium?

Answer 58

Shifts to the right

Question 59

What effect does an addition of a product have on equilibrium?

Answer 59

Shifts to the left

Question 60

What effect does an removal of a reactant have on equilibrium?

Answer 60

Shifts to the left

Question 61

What effect does an removal of a product have on equilibrium?

Answer 61

Shifts to the right

Question 62

What does chromatography do?

Answer 62

Separates compounds according to their relative affinity for the mobile and stationary phases.

Question 63

Why are inert gases used in gas liquid chromatography?

Answer 63

So the sample doesn't react with the gas

Question 64

How do you find the retention factor?

Answer 64

distance travelled by sample/distance travelled by solvent

Question 65

How do you make a standard solution?

Answer 65

Accurately weight the solute (tablet) Dissolve in minimal volume of water Transfer into a volumetric flask Use wash bottle to transfer remains into flask Fill to a known volume(250cm3) with deionised water Invert flask a few times to ensure solution is well mixed