Question

Which combination below will NOT result in a chemical reaction?

Answer 1

\[K _{2}SO _{4} +NH _{4} Cl \rightarrow \]
\[CaCl _{2} + AgNO _{3}\rightarrow \]
\[FeBr _{2} + NaOH \rightarrow \]

Answer 2

These reactions are funny but there's an elephant in the room among them. those are both soluble in water, could you tell me why this isn't okay?

In the bottom reactions from memory Iron and Ag silver are insoluble in water, based on the solubility rules which you can't get around from memorizing. these will occur