Question

What determines whether a chemical reaction leads to etching versus deposition/growth for an aqueous and a gas-phase system? Hint: Think about the physical properties of the reaction product in the aqueous and gas-phase.

Answer 1

In case of etching reaction, the starting material tends to loose weight due to etching and the form a solid product. Say etching of glass in presence of fluride anion gives fluorinated silica. In gas-phase as well the etching between solid starting material and gaseous etching reagent always ends up into a solid product. Whereas, in deposition/growth, we would see an increase in the starting material weight after the depsotion or growth has occured. This is thus reverse of the etching process. Generally one of the products formed in this case could be a gas.