# Using solubility guidelines to predict a reaction of two ionic, water-soluble salts

Will a reaction occur in the following case? If so, write a net ionic equation for it:

$$\ce{(NH4)2SO4 (aq) + ZnCl2 (aq) -> ?}$$

The book says that all possible combinations of positive and negative ions lead to water soluble compounds, all of the ions remain in solution. No reactions occur.

Now I am a little confused. Why didn't $$\ce{(NH4)2}$$ join with $$\ce{Cl2}$$ and why didn't $$\ce{SO4}$$ join with $$\ce{Zn}$$? Or did they?

Of course $\ce{NH4+}$ can join $\ce{Cl-}$ and $\ce{Zn^2+}$ can join $\ce{SO4^2-}$, but the formed salts are completely soluble in water, and they completely dissociate in water to gives the corresponding ions.
On the other hand, the starting salts: $\ce{(NH4)2SO4}$ and $\ce{ZnCl2}$ are completely soluble in water, and they completely dissociate in water to gives the corresponding ions.