So I just learned in chemistry that salts are ionic compounds. Shouldn't, $\ce{H+Cl-}$ be a salt since hydrogen ion has positive charge and chloride ion has negative charge? If $\ce{HCl}$ is a salt then why do we call it an acid?

Sorry if my question is stupid.

  • 1
    $\begingroup$ A is B does not generally mean B is A. Salts have ionic structure when in pure form ( or would have if not stable enough to isolate them ). It is not the case of HCl // BTW, a compound can be a salt, an acid and a base at the same time, like solution of KH2PO4. As being a salt, aan acid or a base are different, not excluding behaviour aspects of compounds. $\endgroup$
    – Poutnik
    Sep 16 '21 at 7:36
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    $\begingroup$ Pure $\ce{HCl}$ is not a salt. Pure $\ce{HCl}$ is a gas, and a molecular gas. It is not made of ions. A salt is made of ions. There are no ions in pure $\ce{HCl}$. OTOH, $\ce{HCl}$ does not react with $\ce{CO3}$ $\endgroup$
    – Maurice
    Sep 16 '21 at 9:49
  • $\begingroup$ HCl is not ionic. True, it becomes ionic when dissolved in water, but that's another story. Salts are compounds of metals, and there are no metals in HCl. $\endgroup$ Sep 16 '21 at 11:19
  • $\begingroup$ "Salts are compounds of metals". Like ammonium chloride. OK. 🙄 $\endgroup$ Sep 16 '21 at 15:50

Hydrogen and chlorine atoms of $\ce{HCl}$ in gaseous state are covalently bound and is termed hydrogen chloride. When this gas is bubbled into water, it ionizes completely to give $\ce{H3O+}$ (free proton + water molecule) and $\ce{Cl-}$ ions and becomes an acid solution which is termed hydrochloric acid. Even in gaseous $\ce{HCl}$, the charge is not distributed evenly. The chlorine is partially negative and the hydrogen is partially positive.

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  • $\begingroup$ The free ion $\ce{H+}$ does not exist in water, because it is not an atom : it is a proton, and it is much smaller than an atom. So it is attached to the Oxygen atom of the next water molecule, producing the ion $\ce{H3O+}$ $\endgroup$
    – Maurice
    Sep 16 '21 at 19:05
  • $\begingroup$ @Maurice You are correct. Edited. $\endgroup$ Sep 17 '21 at 3:37

No bond is completely ionic or completely covalent, Fajan's rule. Also $HCl$ is predominantly a covalent compound rather than ionic.

Shouldn't, H+Cl- be a salt since hydrogen is positive and Cl is negative?

Sure, $\ce{HCl}$ does dissociate into $\ce{H+}$ and $\ce{Cl-}$ in a polar solvent, but that doesn't mean $\ce{HCl}$ is simply $\ce{H+}$ and $\ce{Cl-}$. It is largely covalent. Now you can answer your question. Hope that helps.


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