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Edexcel GCSE Chemistry Triple > TOPIC 7 - Rates Of Reaction And Energy Processes > Flashcards

TOPIC 7 - Rates Of Reaction And Energy Processes Flashcards

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1
Q

Rate of reaction

A

A measurement of how fast the reaction happens.

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2
Q

How can rate of reaction be observed?

A

By measuring how quickly the reactants are used up/how quickly the products are formed.

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3
Q

Rate of reaction formula

A

Amount of reaction used up or product formed/

Time

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4
Q

How do you measure precipitation?

A
  1. mix 2 reactant solutions and put flask on paper that has a mark on it.
  2. Observe the mark through the mixture and measure how long it takes for mark to be obscured. Faster disappears= faster reaction.
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5
Q

Why is the observation of precipitation subjective?

A

As different people may not agree on exactly when mark disappears

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6
Q

How do you measure change in mass in a reaction?

A
  1. Measure solution using a mass balance . Quicker the solution drops in mass = faster rate of reaction
  2. Finished when mass stops changing
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7
Q

Safety precautions when measuring change in mass of a reaction.

A

Can put in fume cupboard

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8
Q

How do you observe the volume of gas given off?

A

Use a gas syringe, more gas given off during a set time interval= faster rate of reaction
Is finished when no more gas is produced

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9
Q

Safety precautions when observing volume of gas given off?

A

Use right size gas syringe

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10
Q

How do you measure how surface area affects rate?

A

Use gas syringe, stopwatch, marble chips and hydrochloric acid.
Measure gas given off at set time intervals and record in table
Repeat w same volume/concentration of acid as well as same marble mass but w more crushed marble.
Repeat w powder

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11
Q

Reaction to test for temp’s effect on reaction rate

A

Sodium thiosulfate and hydrochloric acid are heated in a water bath before mixing and placing over black mark.
Time how long it takes to disappear. (Turns yellow)
Can be repeated at different temps.
Quicker disappears= faster rate

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12
Q

Gradient

A

Change in y / change in x

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13
Q

What does the rate of a chemical reaction depend on?

A 
Collision frequency (more successful= faster reaction )
Energy transferred during a collision (need to pass activation energy)
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14
Q

3 factors leading to an increased rate of reaction

A

TEMPERATURE (+temp = +rate)
CONCENTRATION (+concentration = +rate)
SURFACE AREA (+surface area = +rate)

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15
Q

Why does increasing temp increase rate of reaction?

A

Particles move faster so in turn, have more collisions.

Higher temp= increased energy of collisions

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16
Q

Why does increasing concentration increase rate?

A

If a solution is more concentrated, there’s more particles of a reactant in same volume so collisions are more likely.
In a gas, increased pressure crowds particles so collision frequency will increase

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17
Q

Why does increasing surface area contribute to a higher rate of reaction?

A

Increased surface area to volume ratio means the reactants have more area to work on/ collide w.

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18
Q

Catalyst

A

A substance which increases rate of reaction while remaining chemically unchanged.

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19
Q

How do catalysts work?

A

They decrease activation energy by providing an alternative reaction pathway w a lower activation energy.

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20
Q

Enzymes

A

Biological catalysts which catalyse chemical reactions in living cells.
Eg
Respiration, photosynthesis, protein synthesis

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21
Q

Exothermic reaction

A

A reaction which gives out energy to the surroundings, usually in form of heat and is shown by a rise in temp of surroundings

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22
Q

Endothermic reaction

A

One which takes in energy from surroundings, usually in form of heat. Is shown by fall in temp of surroundings

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23
Q

Reaction profile of an exothermic reaction

A

Products are at a lower energy than reactants

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24
Q

Reaction profile of an endothermic reaction

A

Products are at higher energy than reactants

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25
Q

Activation energy

A

The minimum amount of energy needed for bonds to break and for a reaction to start.

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26
Q

What’s the activation energy on a reaction profile?

A

It’s the energy difference between the reactants and the highest point on the curve.

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27
Q

How do you measure change In temperature of a reaction mixture?

A

Put polystyrene cup in beaker of cotton wool (insulation)
Add volume of first reagent to cup.
Measure initial temp.
Add volume of second reagent and stir.
Put lid on cup (reducing energy lost via evaporation)
Record maximum/minimum temp mixture reaches during reaction.
Calculate temp change

28
Q

How do you measure temp changes when dissolving salts in water?

A 
Adding salt to polystyrene cup of water and measuring change in temp when dissolved. 
Eg 
Ammonium chloride (ENDO)
calcium chloride (EXO)
29
Q

What type of reaction are neutralisation reactions?

A

Exothermic

Except ethanoic acid + sodium carbonate

30
Q

What type of reactions are precipitation reactions?

A

Exothermic

31
Q

What happens to bonds during exothermic reactions?

A

They form and energy is released

32
Q

What happens to bonds during endothermic reactions?

A

They break and energy is supplied

33
Q

Formula for overall energy change

A

Overall energy change = energy required to break bonds - energy released by forming bonds

34
Q

Energy change during an endothermic reaction

A

Positive

35
Q

Energy change in an exothermic reaction

A

Negative

36
Q

Reversible reaction

A

One where the products can react w each other to produce the original reactants.

37
Q

Example of reversible reaction

A

The Haber process

N2 +3H2 (><>) 2NH3

38
Q

Where’s the nitrogen obtained from in the haber process?

A

The air (78% nitrogen)

39
Q

Where’s the hydrogen obtained from in the haber process?

A

Hydrocarbon extractions (eg natural gas/oil)

40
Q

How is the haber process carried out?

A

At 450°C w a pressure of 200 atmospheres and an iron catalyst

41
Q

What the catalyst in the haber process?

A

Iron

42
Q

Dynamic equilibrium

A

When the forwards and backward reactions occur simultaneously at the same rate, meaning the concentrations of the reactants and products won’t change.

43
Q

What type of system can a dynamic equilibrium only take place in? Define it?

A

A closed system

One where none of the products/ reactants can escape

44
Q

An equilibrium lying to the right

A

The concentration of products is greater than that that of reactants.

45
Q

An equilibrium lying to the left

A

Concentration of reactants are greater than that of products

46
Q

Le Chatelier’s principle

A

If there’s a change in concentration, pressure or temperature in a reversible reaction, the equilibrium will move to help counteract that change.

47
Q

What happens when you decrease the temperature of a reaction in equilibrium?

A

The equilibrium will shift to the exothermic direction to produce more heat.

48
Q

What happens when you increase the temperature of a reaction in equilibrium?

A

The equilibrium shifts to the endothermic direction to take in heat and so decrease temp.

49
Q

What happens when you increase the pressure of a reaction in equilibrium?

A

The equilibrium will move towards the side that has fewer moles of gas to reduce pressure.

50
Q

What happens when you decrease the pressure of a reaction in equilibrium?

A

The equilibrium moves towards the side w more molars of gas to increase pressure

51
Q

What happens when you increase the concentration of reactants?

A

The equilibrium moves to the right to use up reactants and make more products

52
Q

What happens when you increase concentration concentration of the products?

A

The equilibrium moves to the left to use up products and make more reactants

53
Q

3 main elements/nutrients plants need

A

PNK?
Phosphorus
Nitrogen
Potassium

54
Q

What do fertilisers do?

A

Increase growth/life processes and so increase crop yield.

55
Q

Why are ammonia fertilisers at an advantage to traditional methods of fertilisers?

A

Their element compositions can be controlled and quantity.

Are soluble so can dissolve into soil easily

56
Q

Ammonia + oxygen?

A

Nitric acid

57
Q

Ammonium sulfate use

A

Fertiliser

58
Q

Production of ammonium sulfate

A

NH3 (+) + H2SO4 (2-)&raquo_space; (NH4)SO4

59
Q

Lab production of ammonium sulphate characteristics

A

Raw materials previously prepared
Small scale
Minimal risk
Simple glassware equipment

60
Q

Industrial manufacture of ammonium sulfate production

A

Ammonia from haber process and sulfúrico acid from contact process.
Large furnaces/tanks
Large scale
High concentrated acid w high pressure/temps

61
Q

How much yield does 450°C produce in the haber process?

A

20-40%

62
Q

How much yield does 200 atmospheres of pressure produce in the haber process?

A

20-40%

63
Q

Pressure in haber process, why?

A

200 atmospheres

Any higher is dangerous/expensive

64
Q

Temperature in haber process, why?

A

450°C

Any lower, reaction would be too slow

65
Q

Catalyst in haber process?

A

Iron

Increases rate of reaction

66
Q

Perfect conditions for haber process

A

100°C and 800 atmospheres > 90 % yield

Edexcel GCSE Chemistry Triple (14 decks)

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