Chlorhydric acid ( $HCl$ ) releases in water the hydronium ion ($H_3O^+$, often written as $H^+$) and the chloride ion. Write the equation for that "dissociation"!
$HCl$ $+$ $H_2O$ $\rightarrow$ $H_3O^+$ $+$ $Cl^-$
In water, what state is the copper(II) ion in?
$[Cu(H_2O)_5]^{2+}$
In the test tubes there appears progressively a yellowish colour due to the complex ions trichlorocuprate(II), red, and tetrachlorocuprate(II), yellow. Write the formulas of these complex ions.
$CuCl_3^-$ and $CuCl_4^{2-}$
Write the equations of formation of these ions from the initial state of the aqueous copper ion.
$[Cu(H_2O)_5]^{2+}$ $+$ $3Cl^-$ $\rightarrow$ $[CuCl_3]^{-}$ $+$ $5H_2O$ then: $[CuCl_3]^{-}$ $+$ $Cl^-$ $\rightarrow$ $[CuCl_4]^{2-}$