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IB SQA National 5 Chemistry Unit 3 - Chemistry in Society > Ch 3. Fertilisers > Flashcards

Ch 3. Fertilisers Flashcards

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1
Q

What are the essential elements?

A

The three main elements that plants need to survive.

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2
Q

Identify the three main elements that plants need to survive.

A
  1. Nitrogen (N)
  2. Potassium (P)
  3. Phosphorus (K)
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3
Q

How does Nitrogen benefit a plant?

A

It is needed for plant growth.

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4
Q

How can you tell if a plant has Nitrogen deficiencies?

A

It will have stunted growth and yellow leaves.

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5
Q

How does Potassium benefit a plant?

A

It is needed for respiration and photosynthesis.

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6
Q

How can you tell if a plant has Potassium deficiencies?

A

It will have poor flower and fruit growth.

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7
Q

How does Phosphorus benefit a plant?

A

It is needed for respiration and plant growth.

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8
Q

How can you tell if a plant has Phosphorus deficiencies?

A

It will have poor root growth and discoloured leaves.

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9
Q

What happens to the nutrients/minerals when crops are harvested from the soil?

A

They are removed.

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10
Q

What happens to the soil if the nutrients are not replaced after the crops are harvested?

A

Over time, it will become infertile.

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11
Q

How can the soil be replenished of nutrients?

A

By the use of fertilisers.

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12
Q

What is a fertiliser?

A

A natural or manmade compound which contains one or more of the essential elements needed by plants.

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13
Q

Identify the 4 main compounds found in fertilisers.

A
  1. Ammonium salts
  2. Potassium salts
  3. Nitrates
  4. Phosphates
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14
Q

Why is ammonia a detremental fertiliser?

A

Ammonia is soluble so can be washed away by rainwater into rivers and lakes. This causes pollution, resulting in the death of aquatic life due to the formation of algal blooms (bacterial growth).

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15
Q

What is ammonia? Give its chemical formula.

A

Nitrogen Hydride. NH3.

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16
Q

What is the difference between ammonia and ammonium?

A

Ammonia has 3 Hydrogens, whereas Ammonium has 4.

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17
Q

What are the chemical properties of ammonia?

A
  1. It is a pungent gas
  2. It is soluble in water
  3. It has a trigonal pyramidal shape.
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18
Q

How is ammonia made?

A

Via the Haber Process.

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19
Q

What is the Haber process?

A

A process used to make ammonia by combining very unreactive nitrogen gas with hydrogen gas using high pressure and an iron catalyst.

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20
Q

Give the equation for the Haber process and balance it.

A

N2 + 3H2 (g) = 2NH3 (g)

*Note that the equals sine is actually a two way arrow.

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21
Q

What does a two way arrow show us in an equation?

A

That the reaction is reversable.

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22
Q

Why would’nt a Moderate/Low temperature be used in the Haber process?

A

Because the reaction would be too slow.

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23
Q

What affect would a High temperature (e.g. 450 degrees) have on ammonia in the Haber process?

A

This would cause ammonia to decompose.

24
Q

Why would high pressure be used in the Haber process?

A

This would increase the yield of ammonia.

25
Q

Why would the use of an iron catalyst (Fe) be used in the Haber process?

A

Because it speeds up the production of ammonia, saving energy costs.

26
Q

Why is a condenser used in the Haber process?

A

To cool down the reaction, turning ammonia into a liquid which is easier to extract.

27
Q

Why are the reactants recycled in the Haber process?

A

Unreacted Nitrogen and Hydrogen are returned to the reaction to save money.

28
Q

Draw a diagram of the Haber process.

A

See Notes.

29
Q

How is Nitric acid produced?

A

Via the Ostwald process.

30
Q

What is the Ostwald process?

A

A process used to make Nitric acid. Nitric acid is made commercially by the catalytic oxidation of ammonia (which is used as a feedstock) to make oxides of nitrogen which then dissolve in water to form nitric acid.

31
Q

Is the Ostwald process endothermic or exothermic? How is this helpful?

A

It is exothermic, so heating can be stopped and the heat released will keep the reaction going.

32
Q

Draw a diagram of the Ostwald process.

A

See Notes.

33
Q

Why is ammonia a bad fertiliser?

A

Because it is smelly and alkaline (which can have a negative impact on the plants.

34
Q

What does ammonia being alkaline make possible?

A

When ammonia is a solution (ammonium hydroxide), it can be converted into a soluble salt by neutralisation with an acid.

35
Q

What are nearly all fertilisers?

A

Salts. This makes them more easily dissolved in water.

36
Q

Write the word equation for the neutralisation of ammonia solution.

A

Ammonia solution + acid = ammonium salt + water.

37
Q

Give an examplar word equation of the neutralisation of a certain ammonia solution.

A

Ammonium hydroxide + sulfuric acid = ammonium sulphate + water

38
Q

Give the word equation of the neutralisation of Ammonium hydroxide by sulfuric acid.

A

2NH4OH (aq) + H2SO4 (aq) = (NH4)2SO4 (aq) + 2H2O (l)

39
Q

What do fertilisers provide plants with?

A

Most fertilisers are a mixture of chemicals to provide the correct amount of nutrients for a particular crop.

40
Q

How is ammonium nitrate made?

A

This is one of the worlds most common fertilisers and is made by reacting Ammonium hydroxide with nitric acid.

41
Q

What catalyst is used in the Ostwald process?

A

A platinum catalyst.

42
Q

What is the chemical equation for the Ostwald process?

A

NH3 (g) + 5O2 (g) = 4NO (g) + 6H2O (g)

43
Q

What temperature is the catalyst heated to?

A

600-800 degrees.

44
Q

Looking at the Ostwald process in more depth, what happens at each stage?

A

Stage 1:

The ammonia is reacted with oxygen from the air to produce nitrogen oxide gas (NO) using a platinum catalyst.

Stage 2:

Nitrogen oxide gas reacts with oxygen to produce nitrogen dioxide gas (NO2).

Stage 3:

The NO2 then reacts with water to make Nitric acid.

45
Q

What is the word equation for the Ostwald process in the Absorbtion tower (Stage 2 and Stage 3)?

A

Nitrogen dioxide + water + oxygen = Nitric acid

46
Q

What is the balanced chemical equation for the production of Nitric acid in the Ostwald process (just stage 2 and 3)?

A

4NO2 (g) + 2H2O (g) + O2 (g) = 4 HNO3 (aq)

47
Q

How can ammonia be prepared?

A

By heating any ammonium salt with an alkali (See diagram in notes).

48
Q

What is the formula for an ammonium ion?

A

NH4 ^+

49
Q

How can ammonium ions be tested for?

A

By the production of ammonia gas when a substance is heated with an alkali.

50
Q

What is the word equation of the experiment which shows how ammonia can be prepared?

A

Ammonium chloride + Sodium Hydroxide = Sodium Chloride, Water and Ammonia gas.

51
Q

What is the chemical equation for the experiment which shows how ammonia can be prepared?

A

NH4CL + NaOH = NaCl +H2O + NH3

52
Q

What is the word equation which shows the conversion of ammonia to an acid?

A

Ammonia + water = ammonium hydroxide

53
Q

What is the chemical equation which shows the conversion of ammonia to an acid?

A

NH3 (g) + H2O (l) = NH4^+OH^- (aq)

54
Q

What are the 4 sources of fertilisers?

A
  1. Haber process - to make ammonia (synthetic)
  2. Ostwald process - to make Nitric acid (synthetic)
  3. Decay of dead plants and animals (natural)
  4. Decay of plant and animal waste (natural)
55
Q

Make sure you know how to answer questions on the percentage composition of different nutrients.

A

You can find these questions on bbc bitezise.

IB SQA National 5 Chemistry Unit 3 - Chemistry in Society (4 decks)

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