Ammonium chloride is a white solid which breaks down when heated, to form ammonia and hydrogen chloride. When these two gases are cool enough, they react together to form ammonium chloride again. It is a reversible reaction, which could reach dynamic equilibrium in a closed system.
NH4Cl(s) ⇌ NH3(g) + HCl(g)
It has many different uses, including for fertilizers, manufacturing personal cleansing products, fireworks, a component in metalwork, medicine, as a flavouring agent in the food industry, and as electrolyte in zinc-carbon batteries. It can also be used for decreasing temperatures in cooling showers. However, the most interesting use by far, is by large squid species. They actually use ammonium chloride for flotation. Most fish have an air-filled sac called the swim bladder to control their buoyancy. The swim bladder varies the pressure inside the fish’s body, allowing it to sink or rise in the water. But this is not how large squids stay afloat! An ammonium chloride solution is found throughout their bodies, and as it is less dense than sea water, it helps them maintain neutral buoyancy. Weirdly enough, it also makes them taste a little but like liquorice!!
GCSE Scientists – you need to be able to explain what dynamic equilibrium is, and the factors affecting it. For help with this try our new guide “How to work with the Noble Gases”. It includes information on Le Chatelier’s Principle, questions to try, and answers to check your understanding.
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