c6 - improving reactions + organic chemistry + earth systems

what 3 elements do plants need

nitrogen

phosphorus

potassium

what are symptoms of mineral deficiencies for the different elements

nitrogen - poor growth, yellow leaves

phosphorus - poor root growth - discoloured leaves

potassium - poor fruit growth, discoloured leaves

what are fertilisers

substances that replace elements used by plants as they grow that are in water-soluble form so they can be absorbed by plant roots

what are examples of water-soluble minerals and their formulas

nitrate ions NO₃^- / ammonium ions NH₄⁺

phosphate ions PO₄^3-

potassium ions K⁺

what does the haber process do and what is its equation

manufactures ammonia from nitrogen and hydrogen

N_{2 (g)} + 3H_{2 (g)} ⇌ 2NH_{3 (g)}

what are the 3 raw materials used for the haber process

steam, natural gas, air

how is nitrogen and hydrogen manufactured for the haber process

nitrogen - through the fractional distillation of liquefied air

hydrogen - through reacting natural gas with steam

what percent of the haber process is used to make fertilisers

over 80%

what are 4 examples of compounds in fertilisers

ammonium nitrate

ammonium phosphate

ammonium sulfate

potassium nitrate

draw a flow diagram to show how the 4 mineral compounds are made

what are the 3 conditions used for the haber process and what equilibrium yield does this achieve

iron catalyst present

pressure of 200 atmospheres

temperature of 450 celsius

achieves a 30% equilibrium yield

how is the temperature chosen a compromise

its low enough to achieve a reasonable equilibrium and high enough to achieve a reasonable rate of reaction

why is 450 celsius chosen for the haber process

the forward reaction is exothermic so if temperature is increased, equilibrium moves to the reactants and yield decreases

what are the raw materials needed for the contact process

sulfur, air, water

what happens in each of the 3 stages of the contact process (include equations)

stage 1:

sulfur burns in air to produce sulfur dioxide

S _(s) + O_{2 (g)} → SO_{2 (g)}

stage 2:

sulfur dioxide and oxygen react to form sulfur trioxide

2SO_{2 (g)} + O_{2 (g)} ⇌ 2SO_{3 (g)}

stage 3:

sulfur trioxide is converted to sulfuric acid

H₂O _(l) + SO_{3 (g)} → H₂SO_{4 (aq)}

what are the conditions needed for reacting sulfur dioxide and oxygen to form sulfur trioxide in the contact process and what equilibrium yield does this achieve

pressure of 3 atmospheres

temperature of 450 celsius

a vanadium oxide catalyst

the equilibrium yield is about 96%

how are the hazards of reacting sulfur trioxide with water controlled

it’s carried out in 2 steps:

1. sulfur trioxide is passed through concentrated sulfuric acid to form oleum

2. the oleum is added to water so the reaction makes a larger volume of concentrated sulfuric acid

what is the hazard of reacting sulfur trioxide with water

it produces a hazardous acidic mist

how is ethanol made from renewable raw materials

in fermentation using plant sugars

what is the equation for glucose turning into carbon dioxide and ethanol

C₆H₁₂O_{6 (aq)} → 2CO_{2 (g)} + 2C₂H₅OH _(aq)

how is ethanol made from non-renewable raw materials

from crude oil through the hydration of ethene

what is the equation for making ethanol from ethene

C₂H_{4 (g)} + H₂O _(g) ⇌ C₂H₅OH _(g)

what is yeast

single-celled fungi containing enzyme that catalyse the conversion of glucose to ethanol

why is fermentation carried out at 35 degrees celsius

if the temperature is above 50 enzymes will denature and if it’s too low they will go inactive

what conditions is the hydration of ethene done at

300 degrees celsius

60 atmospheres

phosphoric acid catalyst

what is an ore

a rock or mineral that contains enough metal to make it economical to extract the metal
(the value of the metal is more than the cost of extracting it)

what are 3 examples of ores and the metals they contain

malachite - copper carbonate

bauxite - aluminium oxide

haematite - iron(III) oxide

what is the reactivity series

potassium

sodium

calcium

magnesium

aluminium

(carbon)

zinc

iron

tin

lead

copper

silver

gold

platinum

what are the 2 ways copper can be extracted from copper(II) sulfide

by heating it with methane or hydrogen

OR

1. roast the copper(II) sulfide in air

2. heat the copper(II) oxide with carbon

how are copper or iron extracted

by heating their compounds with carbon or carbon monoxide

when is electrolysis used for extraction

when the metal is more reactive than carbon

draw a diagram of a blast furnace

what is added to a blast furnace

iron ore, coke, limestone to the top

hot air is forced in at the bottom

what is coke

mostly carbon made by heating coal in the absence of air

what happens in a blast furnace (5)

1. coke burns in hot air making carbon dioxide

2. more coke reduces the carbon dioxide to carbon monoxide

3. carbon monoxide reduces iron(II) oxide to iron at 1500 celsius

4. molten iron and impurities (which are removed with limestone) trickle downwards

5. they are then removed separately from the bottom of the furnace

how does limestone remove impurities (2)

1. calcium carbonate (limestone) decomposes to form calcium oxide and carbon dioxide

2. calcium oxide reacts with silica from impurities to form calcium silicate (slag)

how is aluminium found in nature

as aluminium oxide in bauxite ore

how is aluminium extracted

through electrolysis after dissolving it in molten cryolite

why does electrolysis need to be used

because aluminium is more reactive than carbon so cant be displaced

why is cryolite used

because the aluminium oxide must be in liquid form for electrolysis but its boiling point is too high normally so cryolite reduces it

what is the electrolysis cell for the electrolysis of aluminium like

the cell is made from steel and has a graphite inner lining which acts as the cathode

a series of large graphite blocks act as the anode

what happens during the electrolysis of aluminium oxide

aluminium is produced at the cathode

oxygen is produced at the anodes

oxygen reacts with hot graphite anodes and makes carbon dioxide

what are the half equations for the electrolysis of aluminium oxide

cathode - Al ³⁺ + 3e^- → Al

anode - 2O^2- → O₂ + 4e^-