Q:

pH of solution after adding SiCl4

Why is it that adding $\ce{SiCl4}$ will cause the pH of a solution to become acidic? I thought that only salts (ionic bonds break in water) can change the pH once dissolved in water. $\ce{SiCl4}$ has covalent bonds, so why does the pH change?

A:

Silicon is very oxophilic and $\ce{SiCl4}$ irreversibly hydrolyzes in water as follows:
$$\ce{SiCl4_{(l)} + 4 H2O_{(l)} -> 4 HCl_{(aq)} + Si(OH)4_{(s)}} $$
The release of $\ce{HCl}$ creates hydrochloric acid and lowers the pH.

