C6.1 - Improving Processes Flashcards
List 3 essential nutrients/minerals plants need to grow & repair
- Nitrogen (N)
- Phosphorus (P)
- Potassium (K)
Name the essential plant nutrients/minerals & typical symptoms of their deficiency
- Nitrogen = poor growth, yellow leaves
- Phosphorus = poor root growth, discoloured leaves
- Potassium = poor fruit growth, discoloured leaves
Fertilisers
= substances that replace elements used by plants as they grow
NPK fertilisers
= fertilisers that provide nitrogen, phosphorus, potassium in water-soluble compounds
Why is it important for these nutrients to be in the water-soluble form
As plant roots can only absorb them in this way
Osmosis
List the compounds in the water-soluble form for each essential element
- nitrogen = nitrate ions (NO3-) / ammonium ions (NH4+)
- phosphorus = phosphate ions (PO43-)
- potassium = potassium ions (K+)
Haber process
= industrial process to make ammonia
Manufactures ammonia from nitrogen & hydrogen
Write the word and symbol equation for the reaction in the haber process
Nitrogen + hydrogen —> ammonia (exothermic)
N2(g) + 3H2(g) —> 2NH3(g)
what are the raw materials for the haber process
- air
- natural gas
- steam
How do the raw materials make nitrogen & hydrogen
- Nitrogen: manufactured by fractional distillation of liquified air
- Hydrogen: manufactured by reacting natural gas (methane) with steam
Conditions chosen for the haber process
- pressure: 200 atmospheres (20MPa)
- temperature: 450ºC
- iron catalyst
Why is the equilibrium yield of ammonia for the chosen conditions in the haber process only 30%
Perfect equilibrium position for temp & pressure
- to increase pressure pressure = too hazardous & expensive
- to decrease temp = too slow rate of reaction, compromise temp
What increases the overall yield of ammonia to 97% in the haber process
Mixture of gases leaving the reaction vessel is cooled = ammonia is liquified
Allows:
- ammonia to be removed
- unreacted nitrogen & hydrogen to be recycled
List the word equations to make the compounds made in a fertiliser factory
- ammonia + nitric acid —> ammonium nitrate
- ammonia + phosphoric acid —> ammonium phosphate
- ammonia + sulfuric acid —> ammonium sulfate
- ammonium nitrate + potassium chloride —> potassium nitrate
Batch process
Chemical process that makes products in limited amounts at different times
Continuous process
Chemical process that makes products in large amounts all the time
How are industrial processes different from in the laboratory (for making fertilisers)
Laboratory
- batch process
+ start with pure substances
Industrial (fertiliser factory)
+ continuous process
- start with raw materials, must be purified before or after
How to make potassium sulfate in a lab:
- 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)
How to make ammonium sulfate in a lab
- 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)
What fertiliser compounds are made in industrial processes (fertiliser factory)
- ammonium nitrate, NH4NO3
- ammonium sulfate, (NH4)2SO4
- ammonium phosphate, (NH4)3PO4
- potassium nitrate, KNO3
What fertiliser compounds can be made in a laboratory
- potassium sulfate, K2SO4 (aq)
- ammonium sulfate, (NH4)2SO4 (aq)
What is the contact process
Industrial process to make sulfuric acid
Raw materials needed for the contact process (sulfuric acid)
- sulfur
- air (source of oxygen)
- water
3 stages of the contact process
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
Word & symbol equation for stage 1 of the contact process
Sulfur + oxygen —> sulfur dioxide
S (s) + O2 (g) —> SO2 (g)
(exothermic)
Word & symbol equation for stage 2 of the contact process
Sulfur dioxide + oxygen sulfur trioxide
2SO2 (g) + O2 (g) 2SO3 (g)
(Exothermic)
Conditions chosen for stage 2 of the contact process to make the equilibrium yield 96%
- pressure: 2 atmospheres (200kPa)
- temperature: 450ºC
- vanadium(V) oxide catalyst, V2O5
why is the temperate high even though low temps = high equilibrium yield
- catalyst only works above 380ºC
- achieve reasonable rate of reaction
Word & symbol equation for stage 3 of the contact process
Sulfur trioxide + water —> sulfuric acid
SO3 (g) + H2O (l) —> H2SO4 (aq)
(Exothermic)
Why is stage 3 of the contact process split into 2 steps
As the reaction is very exothermic
So it would produce a hazardous acidic mist
Word & symbol equation for step 1 & 2 of stage 3 of the contact process
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)
How is alcohol (ethanol) made from renewable raw materials
Made from plant sugars using fermentation
What does their fermentation of ethanol rely on & why
= yeast
Contains enzymes that catalyse the reaction
Word & symbol equation for fermentation to produce ethanol
Glucose —> carbon dioxide + ethanol
C6H12O6 (aq) —> 2CO2 (g) + 2C2H5OH (aq)
Why can fermentation be carried out in a lab
Conditions:
- temperature: 35ºC
- normal atmospheric pressure
Why is fermentation carried out at 35ºC
If temp too low: yeast cells become inactive
If temp too high: enzymes in yeast become denatured & stop working (above 50ºC)
how is alcohol (ethanol) made from non-renewable raw materials
- ethene obtained from crude oil
- ethanol produced by hydration of ethene
Word & symbol equation for hydration of ethene
ethene + steam < — > ethanol
C2H4 (g) + H2O (g) < — > C2H5OH (g)
(Exothermic, reversible reaction)
Why is hydration only suitable as an industrial process (not in lab)
Conditions:
- temperature: 300ºC
- pressure: 60 atmospheres
- phosphoric acid catalyst
Advantages of fermentation over hydration
- lower cost of raw materials
- easier conditions
- lower energy requirements
Advantages of hydration over fermentation
- faster rate of reaction
- higher yield (95% compared to 15%)
- higher purity of product, no by-product (fermentation needs filtering & fractional distillation)
