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Chemistry 9-1 iGCSE Oxford AQA > The Rate and Extent of Chemical Change > Flashcards

The Rate and Extent of Chemical Change Flashcards

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1
Q

What is the rate of chemical reaction?

A

Rate of a chemical reaction is how fast the reactants are changed into products

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2
Q

How can a rate of reaction be measured?

A

Rate of reaction = amount of reactant used ÷ time Rate of reaction = amount of product formed ÷ time

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3
Q

What does the rate of a chemical reaction depend on?

A
  • Collision frequency of reacting particles
  • Energy transferred during collision
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4
Q

Explain how the collision frequency of reacting particles effects the a rate of reaction

A

More collisions = faster the reactions

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5
Q

Explain how the energy transferred during collision effects the a rate of reaction

A

Particles have to collide with enough energy for collision to be successful

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6
Q

What is activation energy?

A

Minimum amount of energy needed for particles to react

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7
Q

What is activation energy used for?

A

Particles needs this much energy to break the bonds in reactants (at start of reaction)

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8
Q

Name 4 factors that affect the rate of reaction (excluding collision theory)

A
  • Temperature
  • Concentration of Solution/Pressure of Gas
  • Surface Area
  • Catalyst
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9
Q

Explain how increasing the temperature will increase the rate of a reaction

A
  1. When temperature is increased = particles move faster
  2. Moving faster = collide more frequently
  3. Faster they move = more energy = so more of collision will have enough energy to make reaction happen
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10
Q

Explain how increasing the concentration/pressure will increase the rate of a reaction

A
  1. Solution more concentrated = more particles knocking back in same volume of water (solvent)
  2. Pressure of gas increased = same number of particles occupies smaller space
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11
Q

Explain how increasing the surface area will increase the rate of a reaction

A
  1. If one reactant is solid → breaking it up into smaller pieces = increases surface area to volume ratio
  2. Means same volume of solid = particles around it will have more area to work on → more frequent collisions
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12
Q

Explain how increasing using a catalyst will increase the rate of a reaction

A
  1. They work by decreasing activation energy needed for reaction to occur 2. They do this by providing an alternative reaction pathway with lower activation energy
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13
Q

What is a catalyst?

A

Catalyst is a substance that speeds up reaction WITHOUT being used up in reaction itself

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14
Q

What does it mean if a system is in equilibrium?

A

Forward reaction is going at exactly the same rate as backward one

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15
Q

What is dynamic equilibrium?

A

Both reactions (forward and backwards) are happening but no overall effect = conc. of reactants + products have reached balance and won’t change

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16
Q

When does equilibrium take place?

A

If the reversible reaction takes place in closed system

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17
Q

What is a closed system?

A

Where none of the reactants/products can escape AND nothing can get it in

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18
Q

In reversible reactions, if reaction is endothermic in one direction, the other direction will be…

A

Exothermic (reversible reactions can be endothermic and exothermic)

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19
Q

The position of equilibrium can be on…

A

The right or left

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20
Q

When a reaction is at equilibrium does it mean the amount of reactants = amount of products?

A

NO. When reaction’s at equilibrium it doesn’t mean → amount of reactants = amount of products.

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21
Q

What does it mean if equilibrium lies to the right?

A

Concentration of product > reactants

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22
Q

What does it mean if equilibrium lies to the left?

A

Concentration of reactants > products

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23
Q

What conditions affect the position of equilibrium (excluding the reaction itself)?

A
  • Temperature
  • Pressure (only affects equilibria involving gases)
  • Concentration of reactants and products
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24
Q

What is Le Chatelier’s Principle?

A

It’s the idea that if you change the conditions of a reversible reaction at equilibrium → system will try to counteract change

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25
Q

What can Le Chatelier’s Principle be used for?

A

Can be used to predict effect of any changes you make to reaction system

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26
Q

What happens if you increase the temperature in a reversible reaction in equilibrium?

A

Equilibrium will move in endothermic direction to try and decrease it

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27
Q

What happens if you decrease the temperature in a reversible reaction in equilibrium?

A

Equilibrium will move in exothermic direction to produce more heat

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28
Q

In which reaction would you get more products: in a endothermic reaction or exothermic reaction?

A

More products = endothermic reaction

29
Q

In which reaction would you get fewer products: in a endothermic reaction or exothermic reaction?

A

Fewer products = exothermic reaction

30
Q

What happens if you decrease the pressure in a reversible reaction involving gases in equilibrium?

A

Equilibrium tries to increase it = moves in direction where there’s more gas molecules

31
Q

What happens if you increase the pressure in a reversible reaction involving gases in equilibrium?

A

Equilibrium tries to reduce it = moves in direction where there’s fewer gas molecules

32
Q

What happens if you change concentration of either reactants or products in a reversible reaction in equilibrium?

A

System will no longer be at equilibrium (system will respond by bringing itself back to equilibrium again)

33
Q

What happens if you increase the concentration of reactants in a reversible reaction in equilibrium?

A

System tries to decrease it by making more products

34
Q

What happens if you decrease the concentration of products in a reversible reaction in equilibrium?

A

System tries to increase it again by increasing amount of reactants

35
Q

What is the Haber process used for?

A

To make ammonia from hydrogen and nitrogen

36
Q

What are the reactants in this reaction

A

Hydrogen and nitrogen

37
Q

Why is this reaction is suited for an industrial scale?

A

Reactants aren’t too difficult or expensive to obtain

38
Q

Explain how the reactants aren’t too difficult or expensive to obtain

A
  • Nitrogen is obtained easily form air (which is 78% nitrogen)
  • Hydrogen mainly comes from reacting methane (from natural gas) with steam to form hydrogen and carbon dioxide
39
Q

What are the 3 industrial conditions required in the haber process?

A

Temperature: 450°C

Pressure: 200 atmospheres

Catalyst: iron

40
Q

How is the ammonia produced removed?

A

It cools in condenser & it liquefies and is removed

41
Q

What happens to the unused hydrogen and nitrogen?

A

It’s recycled

42
Q

What is ammonia produced used for?

A

Used to make ammonium nitrate - a very nitrogen-rich fertilisers

43
Q

Is the forward reaction in the Haber process exothermic or endothermic?

A

Forward reaction in the Haber process is exothermic

44
Q

What happens if you increase the temperature in the Haber process?

A

Equilibrium will move (the wrong way) away from ammonia and towards nitrogen and hydrogen

45
Q

Is the yield of ammonia greater at higher or lower temperatures?

A

Lower temperatures

46
Q

What is the problem with lowering the temperature in the Haber process?

A

Lower temperature = slower rate of reaction (equilibrium is reached slower)

47
Q

Why is temperature 450°C used in the Haber process?

A

450°C is compromise between maximum yield and speed of reaction E.g. Better to wait 20 seconds for 10% yield than wait 60 seconds for a 20% yield

48
Q

How does increasing the pressure in the Haber process increase the percentage yield (and rate of reaction)?

A

Higher pressures move position of equilibrium towards products since there are 4 molecules of gas on left-hand side for every 2 molecules on right

49
Q

Why 200 atmospheres the operating pressure in the Haber process not higher?

A

It would make the process too expensive and too dangerous to build and maintain

50
Q

Why is an iron catalyst used in the Haber process?

A

Makes reaction go faster

51
Q

Does an iron catalyst increase the yield in the Haber process?

A

NO, doesn’t affect yield.

52
Q

What is the balanced symbol equation for the Haber process?

A

N2(g) + 3H2(g) ⇌ 2NH3(g)

53
Q

What is the word equation for the Haber process?

A

Nitrogen + Hydrogen ⇌ Ammonia (+heat)

54
Q

What is the contact process?

A

Process for making sulfuric acid

55
Q

What are the raw materials needed to make sulfuric acid?

A

Water, air & sulfur

56
Q

What is stage 1 of the contact process?

A

Sulfur (molten) is burned in dry air (and oxidises) to produce sulfur dioxide

57
Q

What is the word equation for stage 1 of the contact process?

A

sulfur + oxygen → sulfur dioxide

58
Q

What is the balanced symbol equation for stage 1 of the contact process?

A

S(l) + O2(g) → SO2(g)

59
Q

What is stage 2 of the contact process?

A

(In converter) Sulfur dioxide reacts with more oxygen to make sulfur trioxide

60
Q

What is the word equation for stage 2 of the contact process?

A

sulfur dioxide + oxygen ⇌ sulfur trioxide

61
Q

What is the balanced symbol equation for stage 2 of the contact process?

A

2SO2(g) + O2(g) ⇌ 2SO3(g)

62
Q

How much of sulfur dioxide is converted into sulfur trioxide

A

99.5%

63
Q

What is stage 3 of the contact process?

A

Sulfur trioxide reacts with water to make sulfuric acid

64
Q

What is the word equation for stage 3 of the contact process?

A

SO3(g) + H2O(l) → H2SO4(l)

65
Q

What is the balanced symbol equation for stage 3 of the contact process?

A

Sulfur trioxide + water → sulfuric acid

66
Q

Does the contact process work best in high temperatures or low temperatures?

A

High temperatures

67
Q

Name the conditions for the contact process

A

Catalyst: vanadium(V) oxide, V2O5 Pressure: approximately 1-2 atmospheres Temperature: around 450°C

68
Q

What is a reversible reaction?

A

Forwards and backwards reactions occur at same RATE so concentrations/amounts remain constant - occurs in closed system

Chemistry 9-1 iGCSE Oxford AQA (11 decks)

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