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GCSE Chemistry > C6.1 - Improving Processes > Flashcards

C6.1 - Improving Processes Flashcards

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1
Q

List 3 essential nutrients/minerals plants need to grow & repair

A
  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
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2
Q

Name the essential plant nutrients/minerals & typical symptoms of their deficiency

A
  • Nitrogen = poor growth, yellow leaves
  • Phosphorus = poor root growth, discoloured leaves
  • Potassium = poor fruit growth, discoloured leaves
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3
Q

Fertilisers

A

= substances that replace elements used by plants as they grow

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4
Q

NPK fertilisers

A

= fertilisers that provide nitrogen, phosphorus, potassium in water-soluble compounds

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5
Q

Why is it important for these nutrients to be in the water-soluble form

A

As plant roots can only absorb them in this way

Osmosis

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6
Q

List the compounds in the water-soluble form for each essential element

A
  • nitrogen = nitrate ions (NO3-) / ammonium ions (NH4+)
  • phosphorus = phosphate ions (PO43-)
  • potassium = potassium ions (K+)
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7
Q

Haber process

A

= industrial process to make ammonia

Manufactures ammonia from nitrogen & hydrogen

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8
Q

Write the word and symbol equation for the reaction in the haber process

A

Nitrogen + hydrogen —> ammonia (exothermic)

N2(g) + 3H2(g) —> 2NH3(g)

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9
Q

what are the raw materials for the haber process

A
  • air
  • natural gas
  • steam
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10
Q

How do the raw materials make nitrogen & hydrogen

A
  • Nitrogen: manufactured by fractional distillation of liquified air
  • Hydrogen: manufactured by reacting natural gas (methane) with steam
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11
Q

Conditions chosen for the haber process

A
  • pressure: 200 atmospheres (20MPa)
  • temperature: 450ºC
  • iron catalyst
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12
Q

Why is the equilibrium yield of ammonia for the chosen conditions in the haber process only 30%

A

Perfect equilibrium position for temp & pressure

  • to increase pressure pressure = too hazardous & expensive
  • to decrease temp = too slow rate of reaction, compromise temp
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13
Q

What increases the overall yield of ammonia to 97% in the haber process

A

Mixture of gases leaving the reaction vessel is cooled = ammonia is liquified
Allows:
- ammonia to be removed
- unreacted nitrogen & hydrogen to be recycled

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14
Q

List the word equations to make the compounds made in a fertiliser factory

A
  • ammonia + nitric acid —> ammonium nitrate
  • ammonia + phosphoric acid —> ammonium phosphate
  • ammonia + sulfuric acid —> ammonium sulfate
  • ammonium nitrate + potassium chloride —> potassium nitrate
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15
Q

Batch process

A

Chemical process that makes products in limited amounts at different times

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16
Q

Continuous process

A

Chemical process that makes products in large amounts all the time

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17
Q

How are industrial processes different from in the laboratory (for making fertilisers)

A

Laboratory
- batch process
+ start with pure substances

Industrial (fertiliser factory)
+ continuous process
- start with raw materials, must be purified before or after

18
Q

How to make potassium sulfate in a lab:

A
  • put dilute potassium hydroxide solution (KOH) into conical flask
  • add few drops phenolphthalein indicator
  • add dilute sulfuric acid (H2SO4) from burette / dropping pipette (stop when indicator changes pink to colourless)
  • add ‘activated charcoal’ & filter mixture to remove charcoal & attached phenolphthalein
  • warm filtrate to evaporate water, leaving potasssium sulfate

(Sulfuric acid titrated with potassium hydroxide)

19
Q

How to make ammonium sulfate in a lab

A
  • place dilute ammonia solution (NH3) in conical flask
  • add few drops methyl orange indicator
  • add dilute sulfuric acid (H2SO4) from burette / dropping pipette (stop when indicator changes yellow to red)
  • when end-point reached, add extra ammonia solution to ensure reaction complete
  • remaining ammonia will evaporate

(Sulfuric acid titrated with ammonia solution)

20
Q

What fertiliser compounds are made in industrial processes (fertiliser factory)

A
  • ammonium nitrate, NH4NO3
  • ammonium sulfate, (NH4)2SO4
  • ammonium phosphate, (NH4)3PO4
  • potassium nitrate, KNO3
21
Q

What fertiliser compounds can be made in a laboratory

A
  • potassium sulfate, K2SO4 (aq)

- ammonium sulfate, (NH4)2SO4 (aq)

22
Q

What is the contact process

A

Industrial process to make sulfuric acid

23
Q

Raw materials needed for the contact process (sulfuric acid)

A
  • sulfur
  • air (source of oxygen)
  • water
24
Q

3 stages of the contact process

A

1: sulfur burns in air to produce sulfur dioxide
2: sulfur dioxide & oxygen react together to produce sulfur trioxide
3: sulfur trioxide converted to sulfuric acid

25
Q

Word & symbol equation for stage 1 of the contact process

A

Sulfur + oxygen —> sulfur dioxide

S (s) + O2 (g) —> SO2 (g)

(exothermic)

26
Q

Word & symbol equation for stage 2 of the contact process

A

Sulfur dioxide + oxygen sulfur trioxide

2SO2 (g) + O2 (g) 2SO3 (g)

(Exothermic)

27
Q

Conditions chosen for stage 2 of the contact process to make the equilibrium yield 96%

A
  • pressure: 2 atmospheres (200kPa)
  • temperature: 450ºC
  • vanadium(V) oxide catalyst, V2O5
28
Q

why is the temperate high even though low temps = high equilibrium yield

A
  • catalyst only works above 380ºC

- achieve reasonable rate of reaction

29
Q

Word & symbol equation for stage 3 of the contact process

A

Sulfur trioxide + water —> sulfuric acid

  SO3 (g)      + H2O (l) —> H2SO4 (aq)

(Exothermic)

30
Q

Why is stage 3 of the contact process split into 2 steps

A

As the reaction is very exothermic

So it would produce a hazardous acidic mist

31
Q

Word & symbol equation for step 1 & 2 of stage 3 of the contact process

A

1: sulfur trioxide + sulfuric acid —> oleum compound
SO3 (g) + H2SO4 (l) —> H2S2O7 (l)

2: oleum + water —> sulfuric acid (larger concentrated volume)
H2S2O7 (l) + H2O (l) —> 2H2SO4 (aq)

32
Q

How is alcohol (ethanol) made from renewable raw materials

A

Made from plant sugars using fermentation

33
Q

What does their fermentation of ethanol rely on & why

A

= yeast

Contains enzymes that catalyse the reaction

34
Q

Word & symbol equation for fermentation to produce ethanol

A

Glucose —> carbon dioxide + ethanol

C6H12O6 (aq) —> 2CO2 (g) + 2C2H5OH (aq)

35
Q

Why can fermentation be carried out in a lab

A

Conditions:

  • temperature: 35ºC
  • normal atmospheric pressure
36
Q

Why is fermentation carried out at 35ºC

A

If temp too low: yeast cells become inactive

If temp too high: enzymes in yeast become denatured & stop working (above 50ºC)

37
Q

how is alcohol (ethanol) made from non-renewable raw materials

A
  • ethene obtained from crude oil

- ethanol produced by hydration of ethene

38
Q

Word & symbol equation for hydration of ethene

A

ethene + steam < — > ethanol
C2H4 (g) + H2O (g) < — > C2H5OH (g)

(Exothermic, reversible reaction)

39
Q

Why is hydration only suitable as an industrial process (not in lab)

A

Conditions:

  • temperature: 300ºC
  • pressure: 60 atmospheres
  • phosphoric acid catalyst
40
Q

Advantages of fermentation over hydration

A
  • lower cost of raw materials
  • easier conditions
  • lower energy requirements
41
Q

Advantages of hydration over fermentation

A
  • faster rate of reaction
  • higher yield (95% compared to 15%)
  • higher purity of product, no by-product (fermentation needs filtering & fractional distillation)

GCSE Chemistry (10 decks)

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