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Higher Chemistry - 2021/2022 Version 2 > Unit 3 - Chemistry in Society > Flashcards

Unit 3 - Chemistry in Society Flashcards

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1
Q

What are industrial process designed to do?

A

Maximise profit

Minimise impact on environment

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2
Q

What are the five factors affecting process design?

A 
Availability, sustainability and cost of feedstocks
Opportunities for recycling
Energy requirements
Marketability of by-products
Product yield
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3
Q

What is a raw material?

A

An organic/natural substance

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4
Q

Give an example of a raw material.

A

Metal ores
Oxygen
Fossil fuels

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5
Q

What is a feedstock?

A

What we can get from a raw material

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6
Q

Give an example of a feedstock?

A

Iron

Crude Oil

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7
Q

What is the formula to find mass in grams?

A

m = n x gfm

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8
Q

What is the formula to find number of moles?

A

n = c x v

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9
Q

How do you scale products and reactants?

A

Divide by original no, times by new number

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10
Q

Why are percentage yields carried out?

A

To ensure the production is economically viable

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11
Q

How do you calculate the percentage yield?

A

Balance
Scale
= Theoretical
% = Actual/Theoretical x 100

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12
Q

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

A

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

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13
Q

Why atom economy calculated?

A

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

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14
Q

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

A

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

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15
Q

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

A

Temperature
Particle size/surface area
Concentration
Catalysts

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16
Q

What is activation energy?

A

The minimum quantity of energy required to start a reaction

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17
Q

What increases the rate of reaction?

A

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

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18
Q

Why does increasing concentration increase the rate of reaction?

A

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

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19
Q

Why does increasing the temperature increase the rate of reaction?

A

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

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20
Q

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

A

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

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21
Q

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

A

Graph moves to the left and the peak is higher

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22
Q

How do catalysts increase the rate of reaction?

A

By lowering the activation energy

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23
Q

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

A

Move the activation energy line towards the y axis

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24
Q

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

A

Correct collision geometry

Kinetic energy equal to or greater than the activation energy

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25
Q

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

A

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

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26
Q

How do you calculate the rate of reaction?

A

R = 1/t

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27
Q

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

A

Reactants line to peak of curve

28
Q

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

A

Products line to peak

29
Q

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

A

Reactants line to products line

If exothermic, will be negative

30
Q

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

A

Products line to reactants line

If endothermic, will be negative

31
Q

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

A

Line from reactants to products with a lower peak

32
Q

Catalysts have no effect on the overall enthalpy change

A
33
Q

What are the three stages of catalyst mechanism?

A

Adsorption
Reaction
Desorption

34
Q

What occurs during adsorption?

A

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

35
Q

What occurs during reaction in catalyst mechanism?

A

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

36
Q

What occurs during desorption?

A

The product molecules leave the catalyst

The active site can be occupied again to restart the process

37
Q

What is the activated complex?

A

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

38
Q

What is the equation for volume?

A

V = n x MV

39
Q

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

A 
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
40
Q

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

A 
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
41
Q

What is the enthalpy of combustion?

A

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

42
Q

How do you work out the enthalpy of combustion?

A

E = c x m x delta T

Scale up to one mole

43
Q

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

A 
Start temperature of water
End temperature of water
Start mass of spirit burner
End mass of spirit burner
Volume of water
44
Q

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

A

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

45
Q

What is Hess’s Law?

A

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

46
Q

How do you write Hess’s Law calculations?

A

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

47
Q

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

A

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

48
Q

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

A

Equal

49
Q

When are the concentrations of products and reactants constant?

A

At equilibrium

50
Q

On a concentration graph, where does equilibrium occur?

A

When the two lines level off

51
Q

On a rate graph, where does equilibrium occur?

A

When the two lines meet

52
Q

What are the three ways to shift equilibrium?

A

Changing concentration
Changing temperature
Changing pressure

53
Q

Catalysts do not have an effect on equilibrium

A
54
Q

What effect does increased temperature have on equilibrium?

A

Favours endothermic reaction

55
Q

What effect does decreased temperature have on equilibrium?

A

Favours exothermic reaction

56
Q

What effect does increased pressure have on equilibrium?

A

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

57
Q

What effect does decreased pressure have on equilibrium?

A

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

58
Q

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

A

Shifts to the right

59
Q

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

A

Shifts to the left

60
Q

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

A

Shifts to the left

61
Q

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

A

Shifts to the right

62
Q

What does chromatography do?

A

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

63
Q

Why are inert gases used in gas liquid chromatography?

A

So the sample doesn’t react with the gas

64
Q

How do you find the retention factor?

A

distance travelled by sample/distance travelled by solvent

65
Q

How do you make a standard solution?

A

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

Higher Chemistry - 2021/2022 Version 2 (3 decks)

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