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c6 (ammonium sulfate (flask holding ammonia solution and indicator,…
c6
ammonium sulfate
flask holding ammonia solution and indicator, burette with sulfuric acid solution
methyl orange indicator to ammonia, makes it yellow
slowly add sulfuric acid until yellow turns red, gently swirl flask as you add, go slowly near the end point
methyl orange yellow in alkalis, red in acids, colour change means all ammonia has been neutralised, made ammonium sulfate solution
solution isn't pure, still has methyl orange in it, for pure crystals, note exactly how much acid to takes, repeat using that volume w/o indicator
for solid crystals, gently evaporate using steam bath until only a bit is left, leave to crystallise, then filter and leave crystals to dry
not used in industry, impractical to use burette and steam baths for large quantities, crystallisation is slow
rusting of iron
redox reaction, will rust in contact with both air and water
rust is a form of hydrated iron(III) oxide
iron + oxygen + water --> hydrated iron(III) oxide
iron loses electrons when it reacts w oxygen, each Fe atom loses 3 electrons to become Fe3+, iron is oxidised
oxygen gains electrons when it reacts w iron, each O atom loses 2 electrons to become O2-, oxygen is reduced
other metals can corrode in oxygen and water to form metal oxides, but only iron forms rust
the reaction
in industry, ammonia made at pressure of 200 atm and high temp of 450 in presence of iron catalyst
higher pressures favour forward reaction (since there are 4 moles of gas on left for every 2 on right)
pressure as high a poss for best yield w/o being too expensive to build
forward reaction is exothermic, inc in temp moves equilibrium wrong way - from ammonia to nitrogen and hydrogen, so yield of ammonia is greater at lower temps
lower temps, lower rate of reaction, so temp is increased for a faster rate
450 is a compromise between max yield and speed of reaction, ammonia formed as a gas, cools in condenser, liquefies and is removed, unused hydrogen and nitrogen recycled, not wasted
ammonia
base, can be neutralised by acids to make ammonium salts, important to world food production, key to many fertilisers
neutralise nitric acid w ammonia = ammonium nitrate, high percentage of nitrogen, ammonia and nitric acid, double dose
ammonium sulfate can be used as fertiliser, neutralise sulfuric acid with ammonia
potassium nitrate also fertiliser, neutralise nitric acid w potassium hydroxide
fertiliser factor carries out several process to make fertilisers, eg ammonia from haber, phosphoric acid from phosphate rock, sulfuric acid using contact or nitric acid
conditions for step 2
bc it's reversible
temp : oxidising sulfur dioxide for sulfur trioxide is exothermic, reduced temp for higher yield, but too slow, so compromise temp of 450 for an acceptable yield quite quickly
pressure : 2 moles of gas on products, 3 on the reactants side, so for higher yield, pressure should be increased, but increasing it is expensive, and equilibrium already lies on right, so not necessary, at or just above atmospheric pressure
catalyst : to increase the rate of reaction a vanadium pentoxide catalyst is used, doesn't change equilibrium position
w fairly high temp, low pressure and catalyst, reaction goes quite quickly without reducing yield too much
haber process
used to produce ammonia, N2(g) + 3H2(g) --> <-- 2NH3(g) + heat
nitrogen from air which is 78% nitrogen
hydrogen from hydrocarbons from sources like natural gas and crude oil
some nitrogen and hydrogen reacts to form ammonia, reaction is reversible, ammonia break down again into nitrogen and hydrogen, reaches equilibrium
contact process
used to make sulfuric acid
make sulfur dioxide, usually by burning sulfur in the air
sulfur + oxygen --> sulfur dioxide
S(s) + O2(g) --> SO2(g)
sulfur dioxide oxidised with a catalyst to make sulfur trioxide
sulfur dioxide + oxygen --><-- sulfur trioxide
2SO2(g) + O2(g) --><-- 2SO3(g)
sulfur trioxide used to make sulfuric acid
sulfur trioxide + water --> sulfuric acid
SO3(g) + H2O --> H2SO4
tin plating
coat of tin applied to object eg food cans
tin acts as barrier, stops water and oxygen in air from reaching surface of the metals
only if tin plating remains intact, if scratched to reveal metal below, will start to corrode
sacrificial protection
place a more reactive metal with whatever you don't want to corrode, water and oxygen then react with the sacrificial metal instead
galvanising : coat of zinc put on iron, zinc is more reactive so loses electrons in preference to iron, zinc acts as a barrier, eg steel buckets and corrugated iron roofing
blocks of metal eg magnesium can be bolted to less reactive metals to prevent corrosion, magnesium loses electrons in pref to the less reactive metal, eg ship hulls, underground pipes
iron catalyst
makes reaction go faster, gets it to the equilibrium proportions more quickly
catalyst does't affect equilibrium position ie % yield
w/o catalyst temp would have to be raised more for a quicker reaction, but would reduce the % yield further
fertilisers
3 main essential elements in fertilisers : nitrogen, phosphorus and potassium, plants absorb these nutrients from the soil
if plants don't get enough, growth and life process are affected
fertilisers replace missing elements in the soil or provide more, helps increase crop yield, crops grow faster and bigger
prevention
coat metal w barrier, keeps out water, oxygen or both
painting ideal for large and small structures, oiling or greasing for moving parts like bike chains