What is the name of the acid HCN?

Are you sure that's the correct symbols as that equates to Hydrogen, Carbon and Nitrogen.

Well, it's more commonly known as 'Hydrogen Cyanide' and from the name, I'm sure that you must know that it's a deadly poison and should be handled with care.

It is a compound which dissociates a little and so, is a very weak acid.

HCN \rightleftharpoons H^+ + CN^-

In organic chemistry, we often use it with NaCN (sodium cyanide) or the potassium cyanide to provide CN^- ions for a better reaction yield.

I'll repeat again, extra care should be taken. Use two gloves if possible. It can get through skin and give you a metallic taste in the mouth if touched (a proof that it passes through the skin)

The anhydrous gas HCN is Hydrogen Cyanide, just as the anhydrous gas HCl is Hydrogen Chloride. When dissolved in water the acids are referred to as HYDROCYANIC ACID and Hydrochloric acid, respectively. This is worth pointing out as it explains why CN- is the cyanide ion: it is the salt of a Hydro___ic acid. The other "Ides" are almost always the anion of single atoms: Cl- is chloride, S-2 is sulfide, etc, The exception, CN-, has been known for its toxic properties for so long that it was presumed to be the anion of a new element, It isn't hard to see why - the two atoms are bound so tightly (CN triple bond) that they are hard to see separately. The other common exception to the single atom anion rule is azide ion, (N3)-. It is hard to write here -- be sure you see the difference between Azide and Nitride, N-3, Azide is named in the systematic manner because it is the salt of Hydroazoic acid.

You can start using the LaTeX :)

N_3\ ^-

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