Why do acids ionize in solution if they are covalently bonded? Maybe I am wrong, but I thought acids were covalently bonded since hydrogen doesn't form ionic compounds. For example, wouldn't $\ce{HCl}$ look like:

   

Since the electrons are shared, why does it break into $\ce{H+}$ and $\ce{Cl-}$ in solution?
Because it is energetically favourable ($\Delta{G}&lt;0$) for hydrogen chloride to react with water to form hydronium( $\ce{ H3O+}$) and chloride ions.

Remember that $\ce{ H+}$ does not exist as $\ce{ H+}$ in water, but rather as $\ce{ H3O+}$.