C15: Using resources Flashcards
what is corrosion?
destruction of materials by chemical reactions with substances in the environement
- occurs on surface of metal e.g rusting
how is corrosion prevented?
apply coating that acts as barrier
e.g
- painting
- greasing
- electroplating
rusting chemical reaction?
Iron + Water + oxygen –> hydrated iron oxide
- need water and oxygen for rusting to occur
what is sacrificial protection/galvanising?
- use more reactive metal to coat metal
e.g zinc is used to galvanise iron
- zinc will react with oxygen and carbon dioxide in air /protects iron from corrosion
- Zn –> Zn2+ + 2e-
- zinc loses electrons more easily than iron/ iron recieves these electrons so is reduced , not OXIDISED
how does zinc react with water during the galvanising of iron?
- electrons donated by zinc react wit hydrogen in water producing hydrogen gas
- 2H+ +2e- –> H2
uses of copper alloys?
BRONZE : alloy of copper/tin (used for electrical connectors)
BRASS : alloy of copper and zin (used for tools)
uses of Gold Alloys?
alloys of silver, copper, zinc and gold used for Jewellrey
- othe metals add strength/toughness to gold
uses/properties of aluminium alloys?
low density (used for aircraft)
strong
corrosion resistant
uses/properties of steel alloys?
steel alloys normally mixtures of carbon/iron
- Low carbon steels are easily shaped - used for sheeting
- high carbon steels are hard - used for cutting tools
- stainless steels (have chronimum/nickel) are corrosion resistant - used for cutlery
how are glass ceramics made?
soda lime glass: made by heating a mixture of sand, sodium carbonate, limestone
- on cooling, it soldifies to form GLASS
Borosilicate Glass : MADE FROM SAND/BORON TRIOXIDE
- melts at higher temp than soda lime glass
how are clay ceramics made?
shaping wet clay and heating in a furnace
-used as pottery or bricks –> strong so withsatnd weight/pressure
properties of poylmers and uses?
- good electrical/heat insulators, so good for insulating electrical wiring
how can the same monomer make same polymer with different properties?
- difference in manufacturing process
how do the conditions to make
low density/high density polyethene differ?
LD : HIGH pressure, Moderate temp (low forces of attractions/chains further apart –> low MP/soft)
HD : low temps /pressure , with catalyst (high forces of attrcation/chains closer tgt –> High Mp)
what are thermosoftening polymers?
induvidual chains entwinned with eachother , with WEAK intermolecular forces holding polymer chains tgt
- LOW MP / can be remoulded
what are thermosetting polymers?
strong cross links between monomers on different polymer chains
- strong/rigid - dont melt
what are composites made of and eg?
matrix/ reinforcement
- steel reinforced concrete
( steel - reinforcement , concrete-matrix)
purpose of haber process?
- used to manufacture ammonia , which is used for fertilisers
how are the raw materials for haber process obtained?
NITROGEN : - from air
HYDROGEN : - from natural gas
haber process?
- PURIFIED gases are passed over IRON catalyst at 450 degrees/ 200atm
- some hydrogen/nitrogen react to from ammonia
- on cooling, ammonia liqufies and is removed
- remianing nitrigen/hyrdrogen are recycled
what are ideal conditions for haber process/why are they not used?
IDEAL: N2 + 3H2 –> 2NH3
- high pressure –> equilibrium moves right (less molecules on right) –> more ammonia
- low temps –> FORWARD REACTION IS EXO , so will favour exothermic reaction –> more ammonia
but low temps lead to slow reaction rate/ high pressure needs to much energy
what are NPK fertilisers?
formulatios containing correct ratios of nitrogen, phosphorous, potassium
what salts are used for fertiliers?
Ammonium NITRATE
Calcium PHOSPHATE
POTASSIUM nitrate/sulfate
how can ammonia be used to form ammonium nitrate?
ammonium salts : AMMONIA IS ALKALINE
- neutralises acids forming salts/water
nitric acid : AMMONIA UNDERGOES OXIDATION forming nitric acid
ammonia + nitric acid –> ammonium nitrate
- alkali +acid –> salt
how is potassium nitrate/ sulfate obtained ?
from phosphate rocks
what other salts are used to treat phospate rocks ?
nitric acid : CALCIUM Nitrate + phosphoric acid
- phosphoric acid is neutralised with ammonia to form ammonium phosphate
sulfuric acid: calcium phosphate/sulfate
- single super phosphate
phosphoric acid - calcium phosphate - triple super phosphate
all used to give phosphorous, nitrogen for fertilisers
Why can’t phosphorous rocks be used as fertilisers directly?
Not soluble in water
REQUIRED PRACTICAL: making ammonium sulfate
1) collect 25cm cubed ammonia solution using pippete in conical flask
2) add dilute sulfuric acid , 1cm cubed at a time from burette ( keep swirling)
3) drop small piece of blue litmus in spotting tile and add solution until it goes pink
4) repeat titration until reach 2 concordant results
5) pour solution in evaporating dish /heat over water bath until half of water from solution is evaporated
6) leave rest to evaporate off slowly - leaving crystals
7) pat dry with filter paper
Compare production of fertiliser in lab to industry?
LAB : - made small ‘batch’
- uses glass appartus
- use dilute reactants
FACTORY : - concentrated reactants at 60 degrees
- stainless steel vessels/pipework (withstand high pressure/corrosion
- continuous process
required practical : chromatography
- Use a ruler to draw a horizontal pencil line 2 cm from the end of the chromatography paper
- Use a different capillary tube to put a tiny spot of each colouring A, B, C and D on the line
- Use the fifth tube to put a small spot of the unknown mixture U on the line
- Make sure each spot is no more than 2-3 mm in diameter and label each spot in pencil
- Pour water into the beaker to a depth of no more than 1 cm and clip the top of the chromatography paper to the wooden spill.
- Carefully rest the wooden spill on the top edge of the beaker. The bottom edge of the paper should dip into the solvent
- Allow the solvent to travel undisturbed at least three quarters of the way up the paper
- Remove the paper and draw another pencil line on the dry part of the paper as close to the wet edge as possible. This is called the solvent front line
- Measure the distance in mm between the two pencil lines. This is the distance travelled by the water solvent
- For each food colour A, B, C and D measure the distance in mm from the start line to the middle of the spot
required practical : analysing purification of water samples
- Use the universal indicator paper to
determine the pH of the water sample - Accurately weigh an empty evaporating basin to two decimal places
- Add 25 cm3 of water sample A into the evaporating basin
- Heat the evaporating basin on a tripod and gauze using a Bunsen burner until the solids start to form and the majority of water has evaporated
- Leave for the remaining water to evaporate off
- Weigh the cooled evaporating basin again and calculate the mass of the solids that were dissolved in the water.
