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Higher Chemistry - 2021/2022 > 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 the environment

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2
Q

What are the factors influencing product design?

Hint, there’s 7

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? Give examples

A

An organic/natural substance

Air, Water, Metallic Ores, Fossil Fuels

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4
Q

What is a feedstock? Give examples

A

What we can gain from raw materials

Iron, Crude Oil

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5
Q

What are the three stages of development of new chemicals?

A

Research and development
Pilot Production
Mass Production

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6
Q

Mole triangles?

A

m = n x gfm

n = c x V

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7
Q

How do you calculate the theoretical yield?

A 
Write equation
Balance equation
Write mole ratio
Use information given
Scale up across arrows
(2g ->10g
3g -> (10/2) x 3)
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8
Q

How do you calculate the percentage yield?

A

Work out theoretical yield
Use % = actual yield / theoretical yield x 100
Actual yield should be given in the question

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9
Q

How do you calculate excess?

A

Write equation
Balance equation
Write mole ratio
Use information given to work out the no. of moles for each substance
^ this is what you have
Choose one compound and use mole ratio to scale the other up or down
^this is what you need
Write explanation :
Have ____ moles of ____, need____ moles (of same thing) therefore - _____ is limiting
_____ is in excess

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10
Q

How do you calculate atom economy?

A

Write balances equation
Write mole ratio
Use gfm and mole ratio to work out all the masses
%AE = mass of desired products / TOTAL mass of reactants x 100

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11
Q

What affects the rate of reaction?

A

Particle size / Surface Area
Concentration
Temperature
Catalysts

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12
Q

What is activation energy?

A

The energy required for a successful collision to occur

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13
Q

When would the rate of reaction increase?

A

When more successful collisions occurs. This can be due to:

  • Decreased particle size / increases surface area
  • Increased concentration
  • Increased temperature
  • Use of a catalyst
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14
Q

On a Collision theory graph, what does the peak show?

A

The average kinetic energy of the particles

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15
Q

When does a successful collision occur?

A

When the particles have a kinetic energy equal to or greater than the activation energy

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16
Q

When you increase the temperature, how does the curve on a kinetic energy graph change?

A

Moves to the right and is flatter

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17
Q

General rule for how temperature effects kinetic energy?

A

A small increase in temperature can result in a large increase in the kinetic energy of the particles

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18
Q

How do catalysts increase the rate of reaction?

A

Lower the activation energy for the reaction which allows more particles to have kinetic energy equal to or greater than the ae
^ just move the AE line on the graph backwards.

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19
Q

What two things have to happen in order for a successful collision to occur?

A
  • Correct collision geometry / orientation

- Minimum kinetic energy

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20
Q

How do you calculate the relative rate of a reaction?

A

Rr = 1/t

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21
Q

What does an Exothermic Reaction graph look like?

A 
\_\_\_\_
                    ¦         ¦
                   ¦           ¦
                  ¦             ¦
                 ¦               ¦
--------------¦                 ¦
reactants                    ¦
                                     ¦\_\_\_\_\_\_\_\_\_\_\_\_
                                       products
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22
Q

What does an endothermic reaction graph look like?

A 
\_\_\_\_
                       ¦         ¦
                      ¦           ¦
                     ¦             ¦
                    ¦               ¦\_\_\_\_\_\_\_\_\_\_
                   ¦                  products
                  ¦
                 ¦               
--------------¦                 
reactants
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23
Q

What is the enthalpy change for an endothermic and exothermic reaction?

A

Enthalpy change for exothermic = negative
Enthalpy change for endothermic = positive
Find by calculating the difference in energy between reactants and products

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24
Q

How do you find the activation energy from a reaction pathway graph?

A

Forward Reaction - Difference in energy from reactants to peak of curve
Reverse Reaction - Difference in energy from products to the peak of the curve

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25
Q

How would a reaction pathway graph look if a catalyst was used?

A

Line going from reactants to products but with a flatter curve than the original line

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26
Q

Do catalysts change the overall enthalpy change?

A

No, does not effect the overall enthalpy change

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27
Q

What are the three stages of catalyst activity?

A

Adsorption - reactants temporarily bind to active site of catalyst. Weakens bonds between molecules and activation energy is reduced.
Reaction - Molecules are fixed to the active site so molecules collide with correct geometry
Desorption - Product molecules leave active site. Catalyst is reused as more molecules bind.

(Add, React, Remove)

28
Q

What is the activated complex?

A

Very unstable arrangement of atoms where atoms can either become products or turn back into reactants.
Is a fleeting existence
Occurs at top of peak in graphs.
Can think of a bolder rolling up to the top of a steep hill, could go over or roll back

29
Q

How do you calculate Molar Volume?

A

Balance Equation
Mole ratio
Use gfm to scale
Volume = no. of moles x Molar Volume

30
Q

How do you calculate the enthalpy of combustion?

A

Eh = cmAT
where A= delta or difference

Scale up using the mass of 1 mole compared to burned mass

31
Q

What is enthalpy of combustion?

A

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

32
Q

How would you minimize the energy lost to surroundings while measuring combustion?

A

Draught shield
Minimal distance between container and bunsen burner
Metal calorimeter

33
Q

Why would the data book value for enthalpy of combustion differ from the value calculated in a lab?

A

Energy lost to surroundings
Evaporation of alcohol / time cap was off of burner
Reading uncertainties
Incomplete combustion

34
Q

What information would you require to calculate the enthalpy of combustion?

A

Mass of water (or equivalent)
Change in temperature
Change in mass of spirit burner

35
Q

What is Hess’s Law?

A

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

36
Q

How would you prove Hess’s law?

A

enthalpy change of route 1 = enthalpy chance of route 2 + route 3

37
Q

How would you calculate Hess’s Law equations?

A

Write balanced equation
Write equations for the enthalpy of combustion for expressed elements with their enthalpy change from the data book
Rewrite to scale up or reverse equations - make sure to reverse sign if reversing equation
Combine corrected equation and find the total enthalpy change

38
Q

Bond making is….

A

Endothermic - requires energy

39
Q

Bond breaking is…

A

Exothermic - releases energy

40
Q

What happens at a dynamic equilibrium?

A

When the reaction appears to have stopped because the rates of the forward and reverse reactions are equal

41
Q

At equilibrium, what it the forward rate of reaction equal to?

A

Equal to the rate of the reverse reaction.

Mark on graph when the two lines meet

42
Q

At equilibrium, how would you describe the concentration of products and reactants?

A

Constant
Mark on graph when lines are :
_________
_________

43
Q

Why would chemists shift the position of equilibrium?

A

To increase the product yield

44
Q

How would chemists shift the position of equilibrium?

A

By altering the concentration, the temperature, or the pressure

45
Q

How do you remember how shifting equilibrium works?

A

An unbalanced seesaw that moves its base towards the lightest side to remain at 180 degrees

46
Q

What side is your left?

A

The arm with the watch

47
Q

If the concentration of reactants is increased, how does the equilibrium shift?

A

Shifts towards the right to make more product

48
Q

If the concentration of products is increased, how does the equilibrium shift?

A

Shift to products left (side) to convert products back into reactants

49
Q

How do you structure equilibrium conclusions?

A
  • Addition of ____
  • Increasing/decreasing concentration of ____
  • Equilibrium shifts to the ______
    (- bleaching effect increases/decreases)
    (- turns _____)
50
Q

Do catalysts have an effect on the position of equilibrium, and why?

A

No, only increase rate of the reaction by lowering the activation energy

51
Q

If the temperature is increased, what reaction is favoured?

A

The endothermic reaction

52
Q

If the temperature is decreased, what reaction is favoured?

A

The exothermic reaction

53
Q

How would you find out what reaction is being favoured in terms of temperature?

A
  • Look at enthalpy change sign = if positive, forward reaction is endo, if negative, forward reaction is exo
  • Label forward and reverse arrow
  • See is temp is increasing or decreasing
    If increasing, will favour the endothermic reaction, decide whether that favours the forward or reverse reaction
    If decreasing, will favour the exothermic reaction, decide whether that favours the forward of reverse reaction
54
Q

If the pressure is increased, what happens to the equilibrium?

A

Shifts to the side with the fewest no. of moles of gas

55
Q

If the pressure is decreased, what happens to the equilibrium?

A

Shifts to the side with the fewest no. of moles of gas.

56
Q

What is the balanced equation for the production of ammonia?

A

NH3 + 3H2 2NH3

AH = -91kJmol-1

57
Q

Why is does the Haber Process take place at 400 degrees celcius?

A

High enough to increase the rate of reaction, but any higher and the reverse reaction would be favoured and there wouldn’t be enough products

58
Q

What catalyst is used in the Haber Process, what shape does it have, and why?

A

Iron catalyst
Hollow cylinders
More surface area

59
Q

What is chromatography used to do?

A

Separate the compounds according to how well substances mix.

60
Q

Why are inert gases used in chromatography?

A

So they won’t react with the sample

61
Q

What affects retention time?

A

The mass/size and polarity of a molecule

62
Q

What does a high peak in chemical analysis?

A

Greater abundancy

63
Q

How can substances been identified in chemical analysis?

A

Retention factor

64
Q

How do you calculate retention factor?

A

distance travelled by the spot or sample / distance travelled by solvent

65
Q

How do you make a standard solution?

A

Accurately weight mass of solute (tablet etc)
Dissolve in minimal amount of water
Transfer solution into a volumetric flask
Use deionised water to rinse and transfer all remains from the beaker into the flask
Use deionised water to fill the flask up to a known volume (250cm3)

66
Q

What is the equation for the complete combustion of carbon monoxide?

A

2CO (g) + O2(g) —> 2CO2(g)

67
Q

What is the difference between bond enthalpy and mean bond enthalpy?

A 
Mean bond enthalpy must refer to an
average energy and to a number of
compounds and bond enthalpy must
relate to one compound/diatomic
molecule.

Higher Chemistry - 2021/2022 (2 decks)

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