C6.1 Flashcards
What are the 3 essential elements needed by plants?
Nitrogen
Phosphorus
Potassium
What are the typical symptoms of a plant with nitrogen deficiency?
Poor growth
Yellow leaves
What are the typical symptoms of a plant with phosphorus deficiency?
Poor root growth
Discoloured leaves
What are the typical symptoms of a plant with potassium deficiency?
Poor fruit growth
Discoloured leaves
What are fertilisers?
Substances that replace the elements used by plants as they grow
What are the conditions for plants to absorb elements?
They have to be in a water-soluble form
How would plants absorb nitrogen?
The nitrogen has to be in the form of:
Nitrate ions = (NO3)-
Ammonium ions = (NH4)-
How would plants absorb phosphorus?
Phosphorus in:
Phosphate ions = (PO4)3-
How would plants absorb potassium?
In the form of potassium ions = (K)-
What are NPK fertilisers?
Fertilisers that provide nitrogen, phosphorus and potassium in water-soluble compounds
What are the different fertilisers made in factories?
Ammonium Nitrate
Ammonium Sulfate
Ammonium Phosphate
Potassium Nitrate
What is the formula for ammonium nitrate?
NH4NO3
What is the formula for ammonium sulfate?
(NH4)2SO4
What is the formula for ammonium phosphate?
(NH4)3PO4
What is the formula for potassium nitrate?
KNO3
Which fertilisers can be easily made in a laboratory?
Potassium Sulfate - K2SO4
Ammonium Sulfate - (NH4)2SO4
How do you make potassium sulphate in a lab?
- Put dilute potassium hydroxide - KOH(aq) - in a conical flask and add a few drops of phenolphthalein indicator
- Add dilute Sulfuric acid - H2SO4(aq) - from a pipette, stopping when the indicator turns colourless
- Add ‘activated charcoal’ and filter the mixture
- Warm the filtrate to evaporate the water - leaving the potassium Sulfate behind - don’t heat to dryness
Why is phenolphthalein needed when making potassium Sulfate?
It enables you to determine when the alkali (potassium hydroxide) has been neutralised
What will the indicator colour change be when making potassium Sulfate?
Pink to colourless
What is activated charcoal?
A very fine carbon powder with a lard surface area - absorbs many substances
What does the activated charcoal do when making potassium sulfate?
It attracts the phenolphthalein indicator so you can filter it out with the charcoal
What is the formula for potassium hydroxide solution?
KOH(aq)
What is the formula for sulfuric acid?
H2SO4(aq)
What is the formula for potassium sulfate?
K2SO4(aq)
How do you make ammonium sulfate in a lab?
- Place dilute ammonia solution - NH3(aq) - in a conical flask with methyl orange indicator.
- Add dilute sulfuric acid- H2SO4(aq) - from a pipette, stopping when the indicator changes colour
- Add a little more ammonia solution to ensure the reaction is complete - any remaining ammonia will be lost through evaporation
What are the hazards of making ammonium sulfate in a lab?
Ammonia solution and potassium hydroxide solution are all alkaline - corrosive
Ammonia solution releases a bit of ammonia in the gas state - irritating sharp smell - need to take care to avoid breathing it in
Excess ammonia is given off in gas state when the solution is warmed
What are the features of a batch process (in a lab)?
Rate of production - slow
Relative equipment cost - low
Workers needed - large
Shut-down periods - frequent
Ease of automating the process - low
What are the features of a continuous process (industrially)?
Rate of production - fast
Relative equipment cost - high
Workers needed - small
Shut-down periods - rare
Ease of automating the process - high
What substances would a lab start with (when making something)?
You would start with pure substances from a chemical manufacturer
What substances would a factory start with (when making something)?
They would start with raw materials - need to be purified before use or product must be purified at the end
What are raw materials?
Substances obtained from the ground, air or sea
What is the formula for the Haber process?
Reversible reaction sign needed
N2(g) + 3H2(g) —> 2NH3(g)
What does a positive delta (triangle) H mean in a reaction?
The reaction has absorbed heat from its surrounding
What does a negative delta (triangle) H mean in a reaction?
The reaction has released heat during the reaction
What is the delta (triangle) H for the Haber process?
—93kJ/mol
What are the usual conditions used for the Haber process?
Pressure of 200 atmospheres (20MPa)
Temperature of 450 degrees Celsius
An iron catalyst
What is the equilibrium yield of ammonia in the usual conditions?
30%
What factors determine the pressure of the Haber process?
High pressure would give higher yield however, it is lower because a pressure too high would be hazardous and expensive - compromise
What factors determine the temperature chosen in the Haber process?
Lower temperature would give a higher yield however, it is low enough to achieve a reasonable yield but high enough for a good rate of reaction - iron catalyst works more efficiently above 400 degrees Celsius
How does the yield increase when using the Haber process industrially?
The mixture of gases leaving the vessel is cooled so the ammonia is liquified - ammonia is removed and the uncreated nitrogen and hydrogen are recycled - yield becomes 97%
What is the Contact process?
The process of making sulfuric acid
What are the raw materials needed for the Contact process?
Sulfur
Air - a source of oxygen
Water
What happens in the 3 stages (simple) of the Contact process?
Stage 1 - sulfur burns in air to produce sulfur dioxide
Stage 2 - sulfur dioxide and oxygen react to produce sulfur trioxide (reversible)
Stage 3 - sulfur trioxide is converted to sulfuric acid - not actually what happens
What is the formula for stage 1 of the contact process?
Sulfur + Oxygen —> sulfur dioxide
S(s) + O2(g) —> SO2(g)
Delta (triangle) H = -297 kJ/mol
What is the changes in heat for stage 1 of the contact process?
Delta (triangle) H = -297 kJ/mol
What is the formula for stage 2 of the contact process?
Reversible reaction sign
Sulfur Dioxide + Oxygen —> Sulfur Trioxide
2SO2(g) + O2(g) —> 2SO3(g)
Delta (triangle) H = -144kJ/mol
What is the heat change for stage 2 of the contact process?
Delta (triangle) H = -144kJ/mol
What are the conditions chosen for stage 2 of the contact process?
Pressure of 2 atmospheres (200kPa)
Temperature of 450 degrees Celsius
Vanadium(V) oxide catalyst - V2O5
What is the usual equilibrium yield of stage 2 of the contact process under the usual conditions?
96%
What is the formula for stage 3 of the contact process?
Water + Sulfur trioxide —> sulfuric acid
H2O(l) + SO3(g) —> H2SO4(aq)
What factors affect the pressure chosen in stage 2 of the contact process?
Increase pressure means more sulfur trioxide however, the equilibrium position is already far to the right so there isn’t any need of high pressure - 2 atm is just enough to push the gases through the converter
What factors determine the temperature chosen for stage 2 of the contact process?
Increase of temperature means less sulfur trioxide however, it is compromise - low enough to achieve a good yield and high enough for a good rate of reaction - vanadium(V) oxide catalyst only works above 380 degrees Celsius
What is different about stage 3 of the contact process?
The reaction between sulfur trioxide and water is very exothermic and would produce a hazardous acidic mist so it is carried out in 2 steps
What are the two steps for stage 3 of the Contact process to control the hazards?
- Sulfur trioxide is passed through concentrated sulfuric acid to make a compound called oleum
- Oleum is added to water which then makes a larger volume of concentrated Sulfuric acid
What are the formulae for the 2 steps of stage 3 of the contact process?
- Sulfur trioxide + concentrated sulfuric acid —> oleum
H2SO4(l) + SO3 (g) —> H2S2O7 - Oleum + water —> concentrated Sulfuric acid
H2S2O7 (l) + H2O(l) —> 2H2SO4(aq)
What is the formula for oleum?
H2S2O7(l)
Why might sulfuric acid be bad?
It can pollute the environment and produce acid rain…
How is alcohol made renewably?
Ethanol can be made from plant sugars using fermentation
What is fermentation?
A process that relies on yeast - yeast cells contain enzymes that catalyse the conversion of glucose solution to carbon dioxide and ethanol
What is yeast?
Single-celled fungi
What is the word equation for the renewable production of alcohol?
Glucose —> carbon dioxide + ethanol
What is the symbol equation for the renewable production of alcohol?
C6H12O6(aq) —> 2CO2(g) + 2C2H5OH(aq)
What are the conditions for fermentation of yeast?
35 degrees Celsius at normal atmospheric pressure
Why is fermentation carried out at 35 degrees Celsius?
Yeast cells become inactive if temperature is too low.
Enzymes become denatured and stop working above 50 degrees Celsius
What apparatus would you need for a laboratory method of fermentation?
Conical flask - containing glucose solution and yeast
Delivery tube (with bung)
Boiling tube - with limewater in it - will go cloudy
How is alcohol made from non-renewable raw materials?
Ethanol can be made through the hydration of ethene - which comes from cruise oil - non-renewable raw material
What is the word equation for making alcohol from non-renewable raw materials?
Reversible reaction symbol
Ethene + steam <—> ethanol
What is the symbol equation for making alcohol from non-renewable raw materials?
C2H4(g) + H2O(g) <—> C2H5OH(g)
What is the change of heat during the non-renewable production of ethanol?
Delta (triangle) H = -45kJ/mol
What are the conditions for making ethene non-renewably?
Temperature of 300 degrees Celsius
Pressure of 60 atmospheres
Presence of phosphoric acid
What are the features of the renewable method of making ethanol?
Fermentation of sugars
Cost of raw materials = low
Conditions = moderate temperature and normal pressure
Energy requirements = low
Rate of reaction = low
Percentage yield = low - about 15%
Purity of product = low - needs filtering and fractional distillation
What are the features of the non-renewable method of making ethanol?
Cost of raw materials = high
Conditions = high temperature and pressure
Energy requirements = high
Rate of reaction = high
Percentage yield = high - about 95%
Purity of product = high - no by-products
What is an ore?
A rock or mineral that contains enough metal (or metal compound) to make it economical to extract the metal
What metal compounds are found in malachite?
Copper carbonate
What metal compounds are found in bauxite?
Aluminium oxide
What metal compounds are found in haematite?
Iron(III) oxide
How can all metal be extracted?
Using electrolysis however it is more expensive
How are metals more reactive than carbon extracted?
With electrolysis
How are metals less reactive than carbon extracted?
By heating the compound with carbon or carbon monoxide
What is the reactivity series of metals (descending order)?
Potassium
Sodium
Calcium
Magnesium
Aluminium
(Carbon)
Zinc
Iron
Tin
Lead
Copper
Silver
Gold
Platinum
What is the reducing agent?
The atom than gains oxygen and is oxidised
What are the overall steps for extracting copper for anything?
- Make sure you get a product of copper(II) oxide
- Heat the copper oxide with carbon to produce copper and carbon dioxide
What are the symbol equations for extraction copper from copper(II) sulfide?
- 2CuS(s) + 3O2(g) —> 2CuO(s) + 2SO2(g)
- 2CuO(s) + C(s) —> 2Cu(s) + CO2(g)
What can you heat copper(II) oxide with to reduce it to copper?
Methane
Hydrogen
Carbon
Carbon monoxide
What are the symbol equations for extraction copper from malachite?
- CuCO3(s) —> CuO + CO2(g)
- CuO —> Cu(s) + CO2(g)
What is the apparatus needed for extracting a metal?
Bunsen burner
Reduction tube (on top of Bunsen)
Gas in from left through bung
Excess gas burning on the top right of the tube
Metal compound in centre of the tube
Tube is sideways
How is iron extracted.
It’s extracted from its ore using a large reaction container called a blast furnace
Why raw materials are added to the top of the blast furnace when extracting iron?
Iron ore (haematite)
Coke
Limestone
What is coke?
Mostly carbon - made by heating coal in the absence of air
Why is limestone used in a blast furnace when extracting iron?
To purify the iron
What does a blast furnace look like when extracting iron?
Raw materials in at top
Waste gases out the side
Hot air in near the bottom
Liquid slag out near the bottom left
Liquid iron out the bottom right
What reactions happen in a blast furnace when extracting iron?
Stage 1 - coke burns in hot air, making carbon dioxide
Stage 2 - more coke reduces the carbon dioxide to carbon monoxide
Stage 3 - carbon monoxide reduces iron(III) oxide to iron at 1500 degrees Celsius
What are the equations that happens in a blast furnace when extracting iron?
Stage 1 - C(s) + O2(g) —> CO2(g)
Stage 2 - C(s) + CO2(g) —> 2CO(g)
Stage 3 - 3CO(g) + Fe2O3(s) —> 3CO2(g) + 2Fe(l)
What reactions happen to purify iron in the blast furnace?
- Calcium carbonate decomposes to form calcium oxide and carbon dioxide
- calcium oxide reacts with the silica from sandy impurities to form calcium silicate
What are the symbol equation that happen to purify iron in the blast furnace?
- CaCO3(s) —> CaO(s) + CO2
- CaO(s) —> SiO2(g) —> CaSiO3(l)
What is slag?
Molten calcium silicate and it floats on molten iron to get removed separately
What is the problem when trying to extract aluminium from aluminium oxide?
Aluminium oxide is more reactive than carbon so it must be extracted by electrolysis - only works if the compound is in a solution or melted and aluminium oxide doesn’t dissolve in water and its melting point is very high
How is aluminium oxide electrolysed?
The aluminium oxide is dissolved in molten cryolite to allow electrolysis to occur at 950 degrees Celsius rather than melting aluminium oxide at above 2000 degrees Celsius
What does the electrolysis of aluminium oxide look like?
Carbon anodes at the top, going into aluminium oxide dissolved in molten cryolite.
Molten aluminium at the bottom with a tapping hole at the bottom right to collect it.
Carbon lining of the cell which is the cathode
Insulation as an outer layer
Solid crust above the molten cryolite from the electrolyte
What substances are produced at the electrodes in the electrolysis of aluminium oxide?
Aluminium is produced at the cathode
Oxygen is produced at the anode
What is the half equations at the cathode of the electrolysis of aluminium oxide?
(Al)3+ + 3e- —> Al
What is the half equations at the anode of the electrolysis of aluminium oxide?
(2O)2- —> O2 + 4e-
Why does the carbon anode in the cell need replacing regularly during the electrolysis of aluminium oxide?
The oxygen often reacts with it to form carbon dioxide and 50% of it is lost after each electrolysis
What happens during phytoextraction?
Plants are used to absorb “metal” ions from soil containing low-grade “metal” ore. The plants are then burnt and the “metal” is extracted from the “metal” compounds in the ash
What happens in bioleaching?
Bacteria feed of low-grade “metal” ores. By various process, a solution of “metal” ions, called leachate is formed which then get processed to obtain the “metal”
What are the steps for bioleaching?
- Bacteria oxides iron(II) and sullied ions and use the energy transferred
- Sulfuric acid forms in the presence of water and oxygen
- The Sulfuric acid breaks down copper Sulfate ores and other minerals releasing metal ions including copper(II) ions.
What are the attributes of bioleaching?
Cheaper than traditional mining and processing
Uses ores that contain too little metal for other methods to be profitable - low-grade ores
It is slow
Toxic substances are sometimes produced
Sulfuric acid can sometimes escape into water and soil
The bacteria occur naturally and don’t need special treatment
What are the steps for phytoextraction?
- Crop grows on soil containing metal concentration too low for conventional exploitation
- Plant materials burned
- Small volume of plant ash (bio-ore) containing high concentrations of of target metal is produced.
- Bio-ore smelted to yield metal
How can the crops be changed in phytoextraction?
Complexing angers may be added to enhance metal uptake of crops.
