# How can HCl be liquid if it has a boiling point at -85°C?

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?

• 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. Apr 19 '18 at 17:56
• Thanks, side question; how many acids have this feature? Apr 19 '18 at 20:31
• All acids are essentially some compound dissolved in water. Apr 20 '18 at 0:42
• 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. Apr 20 '18 at 1:05
• Search "Magic acid", that should be fun Apr 20 '18 at 8:03

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: $$\ce{H2CO3(aq) -> CO2(g) + H2O(l)}$$