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