A. Sulcius^1,, E. Griskonis¹, N. Zmuidzinaviciene¹

When redox reactions are studied in the chemistry course, focus is limited to the use of a series of metal activity, electron or electron-ion balance method, and writing of the reaction equations. Students find the redox reactions that occur during the dissolution of metals in acids difficult. Motivated students should be able to solve four problems while studying redox reactions: 1) indicate oxidizing agent and reducing agent; 2) write correct products forming and balance the redox reaction; 3) calculate the electromotive force E⁰ of the redox reaction; 4) indicate the thermodynamic possibility of the occurrence of redox reaction by calculating Gibbs energy ΔG⁰. The proposed improved methodology for studying the reactions of dissolution of metals in acids allows students to systematize and expand knowledge about redox reactions in inorganic chemistry. To improve the assimilation of knowledge about the dissolution of copper in sulfuric acid, mnemonic scheme has been proposed that makes it possible to understand better composition of the products. Copper reacted with concentrated sulfuric acid only when heated and precipitation of black deposit was observed. The amount of black deposit in the acid and on the surface of copper depended on the method and intensity of heating: heating with interruptions or intensive continuous heating. It has been determined, that during copper dissolution in concentrated 96% sulfuric acid two reactions take place (the main and the parallel) and precipitation of black deposit, consisting mainly of Cu₂S and a small amount of Cu₂O, is observed.

high school/introductory chemistry, inorganic chemistry, mnemonics/rote learning, metals, oxidation/reduction, reactions