# When zinc chloride is dissolved in water many complexes are formed. How many complexes are formed and what are they ? What is the complex which has the largest Ka?

## Is ZnCl4 2- also present in ZnCl2 solution?

Nov 25, 2017

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#### Explanation:

We write...

$Z n C {l}_{2} \left(s\right) \stackrel{{H}_{2} O}{\rightarrow} Z {n}^{2 +} + 2 C {l}^{-}$

$Z {n}^{2 +}$ is likely present in solution as ${\left[Z n {\left(O {H}_{2}\right)}_{6}\right]}^{2 +}$, a coordination complex if you like of $Z {n}^{2 +}$; chloride ion might be solvated by $4 - 6$ water molecues....we write $Z {n}^{2 +}$ or $Z n C {l}_{2} \left(a q\right)$ as a shorthand.

In the presence of HIGH concentrations of halide ion....the $\text{tetrachlorozincate}$ ion, i.e. ${\left[Z n C {l}_{4}\right]}^{2 -}$, may be formed...In an aqueous solution of $Z n C {l}_{2}$, the dominant species in solution is ${\left[Z n {\left(O {H}_{2}\right)}_{6}\right]}^{2 +}$, and aquated chloride ion....

I have no data to hand, but the metal complex would probably affect the $p H$ of the solution....

${\left[Z n {\left(O {H}_{2}\right)}_{6}\right]}^{2 +} + {H}_{2} O \left(l\right) r i g h t \le f t h a r p \infty n s {\left[Z n \left(O H\right) {\left(O {H}_{2}\right)}_{5}\right]}^{+} + {H}_{3} {O}^{+}$

A solution of zinc ion would thus probably have a $p H < 7$...