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Chemistry > Reversible reactions and equilibrium > Flashcards

Reversible reactions and equilibrium Flashcards

1
Q

What are reversible reactions?

A

Reactions where products can react to produce the original reactants.

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2
Q

What symbol is used for reversible reactions?

A

=

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3
Q

In a reversible reaction, if one direction is exothermic, what is the other direction?

A

Endothermic.

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4
Q

What happens when ammonium chloride is heated?

A

It turns from a white solid to a colourless gas.

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5
Q

What is the equation for the heating of ammonium chloride?

A

NH4Cl(s) = NH3(g) + HCl(g)

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6
Q

What is the method for heating ammonium chloride?

A

Add ammonium chloride to a boiling tube, loosely fit a mineral wool plug, warm the bottom with a Bunsen burner.

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7
Q

What is produced when hydrated copper sulfate is heated?

A

Anhydrous copper sulfate and water.

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8
Q

What is the equation for the heating of hydrated copper sulfate?

A

CuSO4·5H2O(s) = CuSO4(s) + 5H2O(l)

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9
Q

What color change occurs when hydrated copper sulfate is heated?

A

Blue to white.

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10
Q

What is the method for heating hydrated copper sulfate?

A

Add copper sulfate crystals to a boiling tube, gently heat, and observe the color change.

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11
Q

True or False: The forwards reaction of heating hydrated copper sulfate is exothermic.

A

False.

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12
Q

Fill in the blank: In reversible reactions, if the forwards reaction is endothermic, the backwards reaction is _______.

A

Exothermic.

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13
Q

What happens when a few drops of water are added using a dropping pipette?

A

It turns white to blue.

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14
Q

What type of reaction is heating in the context of dynamic equilibrium?

A

Endothermic.

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15
Q

What is a dynamic equilibrium?

A

When the rate of the forward reaction is equal to the rate of the backward reaction.

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16
Q

What occurs in a closed system that reaches dynamic equilibrium?

A

The concentrations of reactants and products stay the same.

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17
Q

What does it indicate if the equilibrium lies on the left in a reaction A + B = C + D?

A

There is a greater concentration of A + B than C + D.

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18
Q

What does it indicate if the equilibrium lies on the right in a reaction A + B = C + D?

A

There is a greater concentration of C + D than A + B.

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19
Q

What happens to the equilibrium if it moves to the right?

A

More products are formed.

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20
Q

What happens to the equilibrium if it moves to the left?

A

More reactants are formed.

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21
Q

What is Le Chatelier’s Principle?

A

If you change the conditions of a reversible reaction in dynamic equilibrium, the equilibrium moves to minimise the effects of the change.

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22
Q

How does increasing the temperature affect the position of equilibrium?

A

It moves the equilibrium in the endothermic direction to decrease the temperature.

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23
Q

What happens to equilibrium when temperature decreases in an exothermic reaction?

A

Equilibrium moves in the exothermic direction

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24
Q

How does increasing pressure affect equilibrium?

A

Moves equilibrium to the side with fewer gas molecules

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25
Q

What is the effect of decreasing pressure on equilibrium?

A

Moves equilibrium to the side with more gas molecules

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26
Q

What effect does increasing the concentration of a reactant have on equilibrium?

A

Moves equilibrium in the direction that decreases the excess amount added

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27
Q

What occurs when the concentration of a substance in a reaction is decreased?

A

Moves equilibrium in the direction that increases the concentration of that substance

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28
Q

In an exam, what should you state regarding equilibrium shifts?

A

The direction the equilibrium moves, the reason why, and which yield increases

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29
Q

What color do cobalt ions exhibit when joined to water?

A

Pink

30
Q

What color do cobalt ions exhibit when joined to chloride ions?

A

Blue

31
Q

What color results from an equilibrium containing similar amounts of cobalt ions in water and chloride ions?

A

Violet

32
Q

What happens to the color of a cobalt solution when water is added?

A

Becomes pinker

33
Q

What color change occurs when hydrochloric acid is added to a cobalt solution?

A

Goes bluer

34
Q

What is the effect of adding acid to an equilibrium containing chromate complexes?

A

Goes the color of the ion with more hydrogen ions

35
Q

What happens to the color of chromate complexes when alkali is added?

A

Goes the color that has hydroxide on its side

36
Q

What is the role of a catalyst in a chemical reaction?

A

A catalyst speeds up a reaction by providing an alternative reaction pathway with a lower activation energy.

37
Q

Do catalysts affect the position of equilibrium in a reaction?

A

No, catalysts speed up both the forwards and backwards reaction by the same amount and do not change the position of the equilibrium.

38
Q

What are the chosen conditions for the Haber Process?

A
  • High pressure - 200 atm
  • Relatively low temperature - 450 degrees C
  • An iron catalyst
39
Q

Why is high pressure (200 atm) used in the Haber Process?

A

Equilibrium shifts to the right as there are fewer gas molecules, increasing ammonia yield and speeding up the rate of reaction.

40
Q

What are the drawbacks of using very high pressure in the Haber Process?

A
  • Too expensive to maintain safety
  • Too much energy required
41
Q

Why is a relatively low temperature (450 degrees C) used in the Haber Process?

A

Equilibrium shifts to the right in the exothermic direction to increase the temperature, thus increasing ammonia yield.

42
Q

What is a disadvantage of using a temperature that is too low in the Haber Process?

A

The rate of reaction is too slow.

43
Q

What type of catalyst is used in the Haber Process?

A

An iron catalyst.

44
Q

Why is iron used as a catalyst in the Haber Process?

A

Iron is cheap and readily available, even though it isn’t the most effective catalyst.

45
Q

What are the raw materials used in the Haber Process?

A
  • Nitrogen
  • Hydrogen
46
Q

Where is nitrogen sourced from for the Haber Process?

A

From the air.

47
Q

Fill in the blank: A catalyst does not affect the _______ of the reaction.

A

equilibrium

48
Q

True or False: The use of a catalyst in a reaction will change the yield of products.

A

False

49
Q

What is the primary source of hydrogen in the Haber process?

A

Reacting natural gas with steam to form hydrogen and carbon dioxide

This reaction is essential for producing hydrogen needed in the process.

50
Q

What are the main conditions for the Haber process?

A

200 atm, 450°C, iron catalyst

These conditions optimize the reaction between nitrogen and hydrogen to produce ammonia.

51
Q

List the main steps involved in the Haber process.

A
  • Nitrogen and hydrogen are compressed
  • They react in the main reactor
  • Conditions: 450 degrees Celsius, 200 atm, iron catalyst
  • The product mixture is cooled
  • Ammonia liquifies in a cooling tank
  • Hydrogen and nitrogen are recycled as gas

Each step is crucial for efficient ammonia production.

52
Q

Why is the Haber process important?

A

Ammonia is converted to ammonium compounds used in fertilizers

Fertilizers are essential for enhancing crop yield.

53
Q

What do crops need for growth?

A

Nitrogen, phosphorus, and potassium

These nutrients are critical for plant development.

54
Q

Define fertilizers.

A

A formulation - a mixture designed to produce a useful product with a specific composition

Fertilizers improve soil fertility and crop production.

55
Q

How is potassium sourced for fertilizers?

A
  • From potassium chloride
  • From potassium sulfate

Both are mined directly and are soluble in water.

56
Q

What is the source of nitrogen for fertilizers?

A

The Haber process

Ammonia produced is often converted into ammonium nitrate for better nitrogen content.

57
Q

What happens to ammonia in the presence of acids?

A

It forms an ammonium salt

This reaction is utilized to produce ammonium compounds for fertilizers.

58
Q

Fill in the blank: Ammonia can be used directly but is usually converted into _______.

A

ammonium nitrate

This conversion provides a higher nitrogen yield.

59
Q

What is the primary issue with phosphate rock as a nutrient source for plants?

A

It is insoluble and cannot be used by plants as nutrients.

Phosphate rock must be processed to become available for plant use.

60
Q

What are the products of the reaction between phosphate rock and nitric acid?

A

Calcium nitrate and phosphoric acid.

Phosphoric acid then reacts with ammonia to produce ammonium phosphates.

61
Q

What is formed when phosphate rock reacts with sulfuric acid?

A

Single superphosphate, a mixture of calcium sulfate and calcium phosphate.

62
Q

What is the main product of the reaction between phosphate rock and phosphoric acid?

A

Triple superphosphate, mainly calcium phosphate.

63
Q

What is the chemical equation for the reaction of ammonia with sulfuric acid?

A

2NH3 (aq) + H2SO4 (aq) → (NH4)2SO4 (aq)

64
Q

Describe the difference between industrial manufacture and lab preparation of fertilizers.

A

Industrial is larger, faster, continuous, higher concentrations, and very exothermic; lab is smaller, slower, batch process, lower concentrations, and safer.

65
Q

What equipment is typically used for the industrial manufacture of fertilizers?

A

Giant vats.

66
Q

What is a key characteristic of the industrial process for fertilizer production?

A

It is a continuous process as long as raw materials are provided.

67
Q

What method is used in the lab to produce fertilizers?

A

Titration followed by crystallization.

68
Q

Why is the lab method of fertilizer production not used in industry?

A

It is too slow.

69
Q

What type of reactants are used in the lab preparation of fertilizers?

A

Dilute forms of the two reactants.

70
Q

What must be done to apparatus in the lab before starting a new batch of fertilizers?

A

The apparatus must be cleaned.

Chemistry (16 decks)

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