If I test a pure solution of an acid chloride with a pH-meter, will I get a reading of pH 7?
When I add water to it, I know $\ce{HCl}$ gas will form, but this gas will dissolve in water to give an acidic solution.
My main confusion is that we call ethanoyl chloride an "acid" chloride, but is its pure solution acidic?
Answer
An acid chloride is a covalent molecule. It has no pH. If you put a pH electrode into a reactive acid chloride you will dehydrate and acylate its hydrated glass surface ($\ce{#Si-OH}$) and damage its future response when properly used. pH electrodes are stored sitting in buffer or saline solution.
An acid chloride is an oxo-acid whose acidic $\ce{-OH}$ has been replaced with $\ce{-Cl}$. Hydrolysis restores the oxo-acid, displacement makes derivatives. Hydrochloric acid is not an acid chloride.
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