Ammonia Flashcards
Joseph priestly??
prepared ammonia by heating slaked lime. he called it alkaline air.
Claude Berthelot??
studied chemical properties of the gas
Davy??
established basic composition
lab prep of ammonia (using ammonium salts)
ammonium salt (NH4Cl) with an alkali (Ca(OH)2) , releasing CaCl2, H20 and NH3.
why is NH4NO3 not used in lab prep
explosive and decomposes
how and why is ammonia collected
downward displacement of air
1. lighter than air
2. highly soluble in water
why is more weight of alkali used in prep using ammonium salts
to counteract the loss by sublimation of NH4Cl on heating in solid state
why is Ca(OH)2 used in lab prep
cheap and not deliquescent
why is flask kept inclined in lab prep
so that water vapour may not trickle down and crack the hot flask
drying agent used for ammonia
quicklime
V.D of ammonia
8.5
lab prep of ammonia(metal nitrides)
Mg3N2 with warm water, releasing Mg(OH)2 and NH3
precaution of lab prep using metal nitrides
thistle funnel should dip below level of water
why is lab prep using metal nitride rarely used?
nitrides are expensive
what is the process of manufacture of ammonia called?
Haber’s process
Haber’s process
Nitrogen and hydrogen combine in a ratio of 1:3. 2 vols of ammonia is released.
conditions of haber’s process
reversible, exothermic(22,400 cals), decrease in volume
temp: 450-500 degrees
pressure: 200-900 atmos.
catalyst: Fe/Mo
precaution in haber’s process
CO, CO2, H2S poisons the catalyst, so mixture must be free of them
how is ammonia in haber’s process condensed
mixture of NH3, and residual nitrogen and hydrogen is allowed to expand suddenly under high pressure, through a small nozzle into a region of low pressure.
how is nitrogen of haber’s process obtained?
fractional distillation of air
Le Chatelier’s principle
if a reaction is exothermic, it is favoured by lowering the temperature
methods of seperation of ammonia from uncombined nitrogen and hydrogen in haber’s process
- liquefaction- it condenses at -33 degrees, at 8 atmos. p
- dissolving in water- 1 vol. of water dissolves 702 vols. of ammonia, at 20 degrees and 1 atmos. p
physical properties of ammonia
colourless, strong pungent odour, slight alkaline taste
non poisonous, affects respiratory system
freezing point and boiling point of ammonia
freezes: -77.7 degrees
boils: -33.5 degrees