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Is hydrogen chloride in liquid state acidic like hydrochloric acid? I know that hydrochloric acid is hydrogen chloride dissolved in water but I was wondering if liquid hydrogen chloride was also an acidic substance. Is this the same for other acids?

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The problem here is that the question is unintentionally loaded. As is, pH is a terrible measure of acidity or basicity for pure substances or when trying to compare solutions in different solvents. Furthermore, acidity and basicity are far more general concepts than pH. Better measures are pKa and proton affinity, but they too have their limitations.

That said, this is a clear-cut case. In truth, pure hydrogen chloride (gaseous or liquid) is a much stronger acid than aqueous hydrochloric acid. When hydrogen chloride is dissolved in water, it reacts quantitatively to produce hydronium ions $\ce{[H(H_2O)_{n}]^+}$. This is the actual acid present in hydrochloric acid solutions. The fact that this reaction between hydrogen chloride and water is quantitative, fast and very exothermic is a suggestion that the water is taming the acidity of the hydrogen chloride. This is a general phenomenon known as solvent levelling.

The exact factor by which the acidity of hydrogen chloride is reduced when dissolved in water is hard to measure precisely. There are attempts to form universal acidity/basicity scales, such as this article (overview here), which tries to define an absolute pH scale, as follows:

From the authors' data , gaseous hydrogen chloride at a pressure of $\mathrm{1\ bar}$ is an acid with an absolute pH ($\mathrm{pH_{abs}}$) of about 160, which is around 30 orders of magnitude stronger than even the most concentrated aqueous hydrochloric acid solution (pH in water approximately equal to -1), which would correspond to a $\mathrm{pH_{abs}}$ of about 190.

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