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Ammonia - Coggle Diagram
Ammonia
physical properties
- compound of nitrogen and hydrogen with formula NH3
- colourless gas with a pungent smell
- only alkaline gas and turns most red litmus blue (presence of OH- ions)
- 1.7 times less dense than air (collected by upward delivery method)
- cannot be dried using concentrated sulfuric acid (common drying agent) bc it will react to produce ammonium sulfate. suitable drying agents are calcium oxide and quicklime. (BUT NOT FUSED CALCIUM CHLORIDE)
- low bp of -33°C and is easily liquefied (weak intermolecular forces of attraction. little amount of energy absorbed to overcome the forces of attraction)
- very soluble in water. dissolves to form a weak alkali (aq ammonia) --> so ammonia gas cannot be collected over water
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uses of ammonia
85% of manufactured ammonia is used to produce fertilisers (ammonium sulfate, ammonium nitrate, urea) ka nitrogenous fertilisers [NPK fertilisers are fertilisers containing Nitrogen, Phosphorus and Potassium)
ammonium fertilisers cannot be added alongside CaOH, CaO as ammonia would be displaced from ammonium salts, causing wastage of the fertiliser as ammonia gas cannot be utilised by plants
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test for ammonia
place a piece of moist red litmus paper at the mouth of the test-tube. if ammonia is present, the moist red litmus will turn blue. (moist bc water is needed to produced the hydroxide ions which turn the red litmus paper blue)
NB usually need to heat test-tube to drive out ammonia gas (very soluble in water)
thermal dissociation - when ammonium salt decomposes on heating and joins again to give the original compound on cooling (e.g. ammonium chloride)
thermal decomposition - when ammonium salt decomposes on heating and does not join back to give the original compound on cooling (e.g. ammonium carbonate, ammonium sulfate)
if moist red litmus turns blue and then red again, consider Mr of gases produced and rate of diffusion & whether substances recombine on cooling