7. ammonia Flashcards
1
Q
ammonia
A
- created during the haber process
2
Q
essential condition
A
- high temperature of 450°c
- pressure of 200 atm
- presence of iron as a catalyst, in powder form (finely divided)
3
Q
equation
A
N2 (g) + 3H2(g) ⇌ 2NH3(g)
- reversible reaction: doesnt reach 100% completion
- nitrogen and hydrogen mixed in a 3:1 ratio so they can react completely, improving yield
4
Q
nitrogen
A
- obtained from the fractional distillation of liquid air
5
Q
hydrogen
A
- obtained from the catalytic cracking of long chain hydrocarbons from petroleum/crude oil
6
Q
preparations of ammonia in the lab
A
- mixing ammonium salt with an alkali (ammonium salt + alkali = salt + water + ammonia gas)
- sublimation of ammonium chloride
- warming aqueous ammonia/ammonia solution/ammonium hydroxide
- mixing nitrate solution with aluminium foil and group 1 alkali
7
Q
used of ammonia
A
- used to make nitrogenous fertilisers to supply nitrogen element to the soil
- essential for synthesis of amino acids > proteins > essential for plant growth
8
Q
nitrogen in soil (natural)
A
- nitrogen can be added to soil naturally by lightning activities or when plants/animals decay
- urea: common natural nitrogenous fertiliser (NH2)2CO
9
Q
why are nitrogenous fertilisers needed
A
- increasing population, increased demand for food
- insufficient natural fertilisers to grow food to feed population
- nitrate or ammonium salts thus used to add nitrogen element to soil
- nitrate ions absorb directly into plants, ammonium ions first oxidise to form nitrate in soil before they are absorbed
10
Q
concerns
A
- soils may become acidic due to acid rain/overuse of fertilisers and pesticides
- calcium hydroxide added to neutralise acidity in soils
- however, ammonium ion can react with hydroxide ion to form ammonia gas, salt + water
- ammonia gas can escape easily from soil, loss of nitrogen element
- cannot add calcium hydroxide + ammonium fertiliser at the same time
11
Q
calcium carbonate
A
- hence calcium carbonate is added cos it doesn’t react with ammonium ion
- but calcium carbonate is insoluble, hence it doesnt dissolve in water and seep underground
- only neutralises acidity on surface, not as effective
