Section 5: Chemistry in Industry Flashcards
if a metal is reactive, is it harder or easier to extract from a compound than a less reactive one?
harder
what reducing agent is used to separate a metal (that is fairly unreactive) from the oxygen in its oxide? how does it achieve this?
carbon, by displacement, e.g. 2CuO + C –> 2Cu + O2
which 5 metals from the reactivity series are extracted using electrolysis?
Potassium, sodium, lithium, calcium, magnesium
carbon can only be used to extract metals from oxygen (by extraction) when the metal is more/less reactive than the carbon itself?
less
what kind of metals is electrolysis used to extract? (hint: reactivity)
metals that are more reactive than carbon
aluminium is more reactive than carbon. What metho is used to extract it from its ore?
electrolysis
what is the main Aluminium ore?
bauxite
after mining and purifying bauxite, what is the identity of the white powder you are left with?
pure aluminium oxide, Al2O3
What is the symbol for aluminium oxide?
Al2O3
what is the substance used as the electrolyte in the extraction process for aluminium? how?
cryolite- aluminium oxide is dissolved in it
how does cryolite help to lower the cost of aluminium extraction?
reduces the temp. needed to carry out electrolysis, as it has a lower melting point than aluminium oxide, which makes the process cheaper to run
what is cryolite?
a less common ore of aluminium oxide
why must the cryolite be molten?
free electrons are needed for electrolysis to occur
what are the electrodes used in the extraction of aluminium oxide and why?
graphite- a good conductor of electricity
what is the reaction (half equation) that occurs at the NEGATIVE electrode, the cathode, during the extraction of aluminium by electrolysis? what kind of reaction is this?
Al3+ + 3e- –> Al
reduction
what is the reaction (half equation) that occurs at the POSITIVE electrode, the anode, during the extraction of aluminium by electrolysis? what kind of reaction is this?
2O2- –> O2 + 4e-
oxidation
what is a observation you could make when looking at the anode during the electrolysis of aluminium oxide and why?
fizzing; CO2 and O2 gas from the negative O2- ions attracted to the anode and having lost electrons
why is electrolysis expensive? (3)
- Uses a lot of electricity
- Sometimes uses a lot of heat energy- the electrolyte must by molten/a liquid
- The positive electrodes need replacing; they disppear
what is the scientific name and symbol equation for iron ore?
hematite, Fe2O3
how is iron extracted from its ore? give 2 details
by reduction in a blast furnace
what is coke made up of and why is it used in iron extraction?
carbon, for reducing the iron oxide to iron metal
what is the role of limestone in iron extraction?
takes away impurities in the form of slag
what is the symbol equation representing the burning of coke to form carbon dioxide?
C + O2 –> CO2
what is the symbol equation representing the reaction of CO2 with unburnt coke?
CO2 + C –> 2CO
what is the symbol equation showing the reduction of iron ore to iron?
3CO + Fe2O3 –> 3CO2 + 2Fe
what is the word equation showing the reduction of iron ore to iron?
carbon monoxide + iron oxide –> carbon dioxide + iron
what is the main impurity in the extraction of iron in a blast furnace?
sand - silicon dioxide
what is the symbol equation to show the decomposition of limestone by the heat in a blast furnace?
CaCO3 –> CaO + CO2
what does the calcium oxide formed by the decomposition of limestone in a blast furnace react with sand to form? What is the symbol equation to show this?
calcium silicate, or slag
CaO + SiO2 –> CaSiO3
what are 2 uses of cooled slag?
fertiliser, road-building
what is the temperature in a blast furnace?
1500 degrees
what 2 things is aluminium useful for making and which of its properties do they depend on?
- Drink cans/products that come into contact with water; aluminium doesn’t corrode
- Bicycle frames/ aeroplanes/ products where the weight is important; aluminium is less dense than iron
what is the main problem with using iron?
it rusts
why do some of the products containing iron combine it with other metals to form alloys?
to prevent it from rusting, make it harder
what are two alloys of iron and what are their uses?
- Steel: car bodies and gliders
2. Cast iron: manhole covers, cooking pans
why is hot air blown into the blast furnace during iron extraction?
to make the coke burn faster than usual and raise the temp. to 1500
during the fractional distillation of crude oil, what are the bubble caps in the fractionating column for?
to stop the separated liquids fromrunning back down the fractionating column and remixing
do longer hydrcarbons have higher or lower boiling points than shorter chains?
higher
what is the temperature gradient from the bottom to the top during the fractional distillation of crude oil?
hot at the bottom, gradually cooler as you go up
What are the seven fractions in the fractional distillation of crude oil, in order of increasing length of hydrocarbon chain?
Refinery Gases Gasoline Naptha Kerosene (paraffin) Diesel fuel oil bitumen
is fractional distllation a chemical or physical process? why(not)?
physical; no chemical reactions
what are refinery gases used for?
bottled gas, heating, pottery & glass manufacture (clean-burning fuel)
what is gasoline used for?
fuel for cars etc
what is naptha used for?
used to make plastics, dyes, drugs, explosives, paints, and as a feedstock in the chemical industry
what is kerosene (paraffin) used for?
Jet engines, domestic heating, paint solvent
what is diesel used for?
fuel for diesel engines in cars, trucks, trains, boats
what is fuel oil used for?
fuel for big ships, domestic central heating
what is bitumen used for?
road surfacing, asphalt roofs
when is carbon monoxide released into the atmosphere?
when hydrocarbon fuels are burnt without enough oxygen - incomplete combustion
how is carbon monoxide harmful to humans?
combines with haemoglobin to prevent it reacting with oxygen to form oxyhaemoglobin meaning the blood can carry less oxygen around the body. This can lead to fainting, a coma or death
when are sulphur dioxide and nitrogen oxide pollutants released into the atmosphere?
when fossil fuels are burnt
what are the conditions needed for nitrogen oxides to be created? example for when this occurs?
very high temp, high enough for oxygen and nitrogen in the air to react - often in car engines
all rain is slightly acidic. Why is this and what are the symbol and word equations to represent it?
because carbon dioxide in the air reacts with water to produce a mildly acidic solution
CO2 + H2O –> H2CO3
carbon dioxide + water –> carbonic acid
what happens when the pollutant sulfur dioxide reacts with clouds? word/symbol equation?
it forms dilute sulphuric acid, which is quite acidic
2SO2 + O2 + H2O –> 2H2SO4
what is the effect of nitrogen oxides being released into the atmosphere?
nitric acid (which precipitates as acid rain) is formed
what are some harmful effects of acid rain? (4)
- Lakes become acidic causing plants/animals to die
- disrupts eco systems
- kills trees
- damages limestone buildings and stone statues
what is cracking?
splitting up long chain hydrocarbons into shorter ones
what are some properties of long hydrocarbons?
high boiling points, viscous
what are some properties of shorter chain hydrocarbons in comparison to long chain ones?
lower boiling points, much thinner and paler in colour
what is an example of a short-chain hydrocarbon used to make petrol?
octane
what are the required conditions for cracking? (temp, catalysts, state of hydrocarbon)
vaporised hydrocarbons are passed over powdered catalyst at…
TEMPERATURE: 600-700 degrees
CATALYSTs: silica (SiO2) OR alumina (Al2O3)
typically, in cracking…
long-chain alkane molecule —>
shorter alkane molecules + alkenes
what two things does the long-chain dodecane, found in paraffin, thermally decompose to form in cracking?
octane and ethene
are the smaller alkanes produced when cracking paraffin in the lab collected as solids of gases?
solids
how are alkenes collected during the cracking of paraffin in the lab?
as gases they travel down the delivery tube and are collected through water using a gas jar
when are plastics formed?
when small molecules called monomers react to make a polymer
what kind of conditions are needed to make addition polymers? eg low/high pressure
high pressure and a catalyst
what happens in terms of the bonds when alkenes form addition polymers?
the carbon-carbon double bonds open up thanks to the high pressure and a catalyst and polymerise (join hands) to form long saturated chains - polymers
with the help of pressure and a catalyst, what addition polymer does ethane become?
poly(ethene)
what is the repeat unit of a polymer and how is it represented?
the section of the polymer’s displayed formula that is repeated over and over again. Drawn as (repeat unit)n
what do you do to the repeat unit in order to find the monomer that makes it?
add a double bond
what properties does the polymer poly(propene) have and which of its uses depend on these?
tough polymer, but relatively flexible and resistant to heat… useful to make things like kettles, food containers, carpets
what properties does the polymer poly(ethene) have and which of its uses depend on these?
light, stretchable polymer…. useful for making packaging: plastic bags, bottles, food containers
most addition polymers are inert. Why Is this?
because the carbon-carbon double bonds in polymer chains are very strong, and not easily broken
what property of polymers means they don’t biodegrade easily?
they are inert, so can’t easily be broken down by bacteria/other organisms
what is another reason why it is hard to get rid of polymers, other than the fact they don’t biodegrade well?
they can’t be burnt, as this releases toxic gases
what is the haber process used to create, and what is this used for?
ammonia, NH3, used to make fertilisers
how is the nitrogen required for the haber process to occur obtained?
from the air, which is 78% nitrogen
from where is the hydrogen needed for the haber process to occur obtained?
from natural gas, or alternatively from cracking hydrocarbons
what are the industrial conditions needed in the haber process? (pressure, temp, catalyst)
Pressure: 200atm
Temperature: 450 degrees
Catalyst: Iron
why do higher pressures favour the forward reaction in the haber process?
there are more moles of gas (4 times) on the left side than on the right
what will the effect of a high pressure be on the yield of the haber process?
increased pressure will equal higher yield
what is the equation representing the haber process?
N2 + 3H2 2NH3 (reversible reaction)
is the forward reaction for the Haber process exothermic or endothermic? what effect does this have when the temp. is increased?
exothermic, means that increasing the temp. will move the equilibrium the wrong way- to the left- leading to a decrease in % yield
what does the fact that the forward reaction in the Haber process is exothermic tell you about the optimum temp. for the reaction occur in terms of yield?
the yield of ammonia will b greater at lower temperatures
why is the fact that a greater yield of ammonia is produced at lower temperatures an issue in the Haber process?
lower temperatures mean a slower rate of reaction - so equilibrium would be reached slowly…
why is the temp. required for the Haber process fairly high even though lower temperatures favour the forward reaction?
450 degreesC is a COMPROMISE between maximum yield and speed of reaction - (it’s better to wait 20secs for a 10%yield than 60secs for a 20%yield)
in the haber process, how is the ammonia (a gas) separated from the hydrogen and nitrogen?
it liquifies in the condenser and is removed - the N2 and H2 are recycled still in the form of gases as ammonia has a higher condensing temp. than the others
what is the Otswald process used to make?
nitric acid(HNO3) and ammonium nitrate fertiliser
what is needed for the Otswald process?
ammonia
how is ammonium nitrate created from ammonia and nitric acid, and why does this mean it is a good fertiliser?
ammonia is reacted with nitric acid to make ammonium nitrate
it is a very good fertiliser because it has nitrogen from two sources - plants need nitrogen to make proteins
why is ammonium nitrate a more effective fertiliser than organic alternatives?
it helps farmers produce crops from land that otherwise wouldn’t have been fertile enough
what is poly(chloroethene) used to make?
clothes, pipes, insulating electrical cables
what is the contact process used to make?
sulphuric acid
what is the first stage of the contact process and what is the reaction representing this?
forming sulphur dioxide by burning sulphur in air or roasting sulphide ores
S + O2 –> SO2
what is done to the sulfur dioxide produced in the 1st stage of the contact process and what does is formed? (+symbol equation)
it is oxidised with the help of a catalyst to form sulfur trioxide gas
2SO2 + O2 2SO3
what is done to the sulfur trioxide produced in stage 2 of the contact process and what is formed? (+symbol equation)
it is dissolved in concentrated sulfuric acid to form liquid oleum
SO3 + H2SO4 –> H2S2O7
in the final stage of the contact process, how is concentrated sulfuric acid formed from oleum?
oleum is diluted with measured amounts of water to form concentrated sulfuric acid
H2S2O7 + H2O –> 2H2SO4
in the second stage of the contact, sulfur dioxide is oxidised to become sulfur trioxide gas. The equation is 2SO2 + O2 –> 2SO3. This reaction is exothermic. What is the obvious thing to do to the temp. and pressure in order to get the maximum yield? why is this a problem?
reduce the temp, increase the pressure (product has less moles/volume than reactants)
this is a problem because a low temp. means a very slow rate of reaction
what are the conditions needed for the contact process? (temp, pressure, catalyst)
temperature: 450 degrees C
pressure: 2atm
catalyst: vanadium(V) oxide, V2O5
what are the three main uses of sulfuric acid in modern industry?
- phosphate fertilisers to improve the amount of nutrients in the soil
- detergents
- paints - sulfuric acid is used to make titanium dioxide which is a white pigment used in paints
during the electrolysis of brine, what is given off at the cathode?
hydrogen gas
during the electrolysis of brine, what is given off at the anode?
chlorine gas
during the electrolysis of brine, what is left in solution?
NaOH - sodium hydroxide
what three useful products are produced during the electrolysis of brine?
chlorine, hydrogen, sodium hydroxide
what is chlorine used for?
to sterilise water supplies (chlorination) , to make bleach, to make HCl
what is hydrogen useful for?
to make ammonia in the Haber process, to change oils into fats for making margarine
how is sodium hydroxide useful in the chemical industry?
very strong base, used to make soap, bleach, and paper pulp
what kind of polymers are made when a small molecule is released during a reaction?
condensation polymers
describe condensation polymerisation
involves two different types of monomer. These monomers react and bonds form between them, making polymer chains. For each new bond that forms, a small molecule is lost
what is an example of a condensation polymer and what is the small molecule lost?
nylon is the condensation polymer, water is lost
