A visual analogy for metallic deposition

Abstract

The fundamental concept of spontaneous metallic deposition stoichiometry problems is that atoms simultaneously arrive at and depart from the same electrode. For example, when copper is deposited on an iron rod from a copper(II) sulfate solution, iron(II) cations depart from the iron rod at the same time that copper(II) cations arrive at the rod.However, this simultaneity is not easily perceived by students; consequently, a problem such as the one shown below is seldom solved correctly.An iron rod was immersed in an aqueous copper(ll) sulfate solution. After a while it was observed that copper had been deposited on the rod. Later the rod was removed from the solution, dried, and weighed. It was noticed that the rod was 2 g heavier. How many grams of copper were deposited on the rod? SolutionFor mole quantities, the reaction can be written 1 mole Cu2+(aq) + 1 mole Fe(s) *-1 mole Fe2+(aq) 4-1 mole Cu(s)