Shouldn't it at least be boiling? When water reaches its boiling point it makes bubbles, but that doesn't happen with HCl, why?

Did I misunderstand some basic chemistry?

  • 7
    $\begingroup$ Hydrochloric acid is hydrogen chloride gas dissolved in water. We often render the solution as HCl when in reality, only the solute is actually HCl. $\endgroup$ Commented Apr 19, 2018 at 17:56
  • $\begingroup$ Thanks, side question; how many acids have this feature? $\endgroup$
    – Hamzalihi
    Commented Apr 19, 2018 at 20:31
  • $\begingroup$ All acids are essentially some compound dissolved in water. $\endgroup$
    – Frank
    Commented Apr 20, 2018 at 0:42
  • 1
    $\begingroup$ Not really @Frank. There are fluorinated superacids (and even at least one chlorinated one, the "carborane superacid") that do not contain oxygen and can't be water plus anything else. $\endgroup$ Commented Apr 20, 2018 at 1:05
  • $\begingroup$ Search "Magic acid", that should be fun $\endgroup$ Commented Apr 20, 2018 at 8:03

1 Answer 1


All halogen compounds with hydrogen ($\ce{HX}$) are gases at STP except for $\ce{HF}$, which is a liquid (b.p.: $\mathrm{19~^\circ C}$). When dissolved in water, $\ce{HX}$ dissociates to ions ($\ce{H+}$ & $\ce{X-}$), which are readily hydrated by water molecules as $\ce{H+ (aq)}$ and $\ce{X- (aq)}$, hence not exists as a gas any more.

To answer your side question, a lot of gases have this feature. For instance, sulfur trioxide ($\ce{SO3}$) is a gas but gives sulfuric acid ($\ce{H2SO4}$) when it come to contact with water. Similarly, nitric acid ($\ce{HNO3}$) can be considered as an aqueous solution of nitrogen dioxide ($\ce{NO2}$). In reality, during an industrial process, $\ce{NO2}$ react with $\ce{H2O}$ in air to give $\ce{HNO3}$. $$\ce{4NO2(g) + O2(g) + 2H2O(l) -> 4HNO3 (aq)}$$ Exception to this trend is carbonic acid ($\ce{H2CO3}$), which decomposes under ambient conditions: $$\ce{H2CO3(aq) -> CO2(g) + H2O(l)}$$

  • $\begingroup$ $\ce{HNO3}$ is NOT a solution of $\ce{NO2}$ in water, because the nitrogen oxidation number is not the same in $\ce{NO2}$ and in $\ce{HNO3}$. It needs oxygen to produce $\ce{HNO3}$ in water. If oxygen is missing $\ce{NO2}$ gets dissolved in water but it produces a mixture of $\ce{HNO2}$ and $\ce{HNO3}$ according to the equation : $$\ce{2 NO2 + H2O -> HNO2 + HNO3}$$ $\endgroup$
    – Maurice
    Commented Feb 10, 2023 at 21:37
  • $\begingroup$ You are correct. I already has mentioned it in my answer. $\endgroup$ Commented Feb 10, 2023 at 22:12

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