Zinc chloride dissolves readily in water to give  species and some free chloride. Aqueous solutions of  are acidic: a 6 M aqueous solution has a pH of 1. The acidity of aqueous  solutions relative to solutions of other Zn salts (say the sulfate) is due to the formation of the tetrahedral chloro aqua complexes where the reduction in coordination number from 6 to 4 further reduces the strength of the O–H bonds in the solvated water molecules.
In alkali solution, zinc chloride converts to various zinc hydroxychlorides. These include , , , and the insoluble . The latter is the mineral simonkolleite. When zinc chloride hydrates are heated, HCl gas evolves and hydroxychlorides result.
When solutions of zinc chloride are treated with ammonia, various ammine complexes are produced. These include  and on concentration . The former contains the  ion, and the latter is molecular with a distorted tetrahedral geometry. The species in aqueous solution have been investigated and show that  is the main species present with  also present at lower :Zn ratio.