Ammonia, NH3, is a pungent alkaline gas manufactured by the Haber process and used to make nitrogenous fertilisers and nitric acid.
Ammonia is the colourless, pungent, alkaline gas with the formula NH₃, manufactured industrially by the Haber process. Malay: ammonia · Chinese: 氨.
Ammonia is very soluble in water and its solution is a weak alkali, so it turns moist red litmus paper blue. It is in fact the only common alkaline gas, which makes that litmus result a useful identifying test. When it meets hydrogen chloride gas, the two combine to form dense white fumes of ammonium chloride, another way to confirm it. As a base, ammonia reacts with acids to form ammonium salts, which are important nitrogenous fertilisers.
Example. Ammonia is reacted with nitric acid to make ammonium nitrate fertiliser: NH₃ + HNO₃ → NH₄NO₃. It is also oxidised industrially to make nitric acid itself, and it is used in some household cleaning agents. Because plants need nitrogen in a usable form, fertilisers made from ammonia are central to modern agriculture.
Confusion to avoid. Do not confuse ammonia, NH₃, the molecule and gas, with the ammonium ion, NH₄⁺, the positive ion found in ammonium salts and formed when ammonia gains a hydrogen ion in water. Ammonia is a base; the ammonium ion is what remains after that base has accepted a proton.
In exam answers, describe ammonia precisely: a colourless gas with a pungent smell, less dense than air, very soluble in water, and the only common gas that turns moist red litmus blue. That litmus test and the white fumes with hydrogen chloride are the two identifications you are most often asked to state, so learn to write them without hesitation.
Ammonia is the key product of the Haber process and the link between industrial chemistry and the acids, bases and salts you studied earlier, so it appears regularly in SPM Chemistry.
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