Question

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?

Answer 1

Got a text book...?

Explanation:

We write...

`ZnCl_2(s) stackrel(H_2O)rarrZn^(2+) + 2Cl^(-)`

`Zn^(2+)` is likely present in solution as `[Zn(OH_2)_6]^(2+)`, a coordination complex if you like of `Zn^(2+)`; chloride ion might be solvated by `4-6` water molecues....we write `Zn^(2+)` or `ZnCl_2(aq)` as a shorthand.

In the presence of HIGH concentrations of halide ion....the `"tetrachlorozincate"` ion, i.e. `[ZnCl_4]^(2-)`, may be formed...In an aqueous solution of `ZnCl_2`, the dominant species in solution is `[Zn(OH_2)_6]^(2+)`, and aquated chloride ion....

I have no data to hand, but the metal complex would probably affect the `pH` of the solution....

`[Zn(OH_2)_6]^(2+) +H_2O(l) rightleftharpoons[Zn(OH)(OH_2)_5]^(+) +H_3O^+`

A solution of zinc ion would thus probably have a `pH<7`...