Abstract
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 G0. 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.
Highlights
Since mineral or inorganic acids are the most frequently used chemicals in research and industry, one of the most important issues is the interaction of metals with solutions of strong acids
It has been proven that dissolution rate of copper Cu in nitric acid is not controlled entirely by rate of chemical reaction and that it is affected by degree of agitation [4]
The goal of our research is to study thoroughly the copper dissolution reaction in concentrated sulfuric acid and provide students with auxiliary material for a deeper understanding of redox reactions occurring when metals dissolve in strong acids
Summary
Since mineral or inorganic acids (sulfuric H2SO4 and nitric HNO3) are the most frequently used chemicals in research and industry, one of the most important issues is the interaction of metals with solutions of strong acids. In the 19th century, Mendeleev wrote, “No equation expresses everything that, takes place under the action of metals on nitric acid, since always several oxides of nitrogen are formed together or sequentially one after another, depending on the acid strength and temperature.” [1]. It is known, that during dissolution of metals in nitric acid, different gaseous products such as N2O, N2, NO, NO2, NH3 [2], and H2 [3] are formed. Using Fourier transform infrared spectroscopy it has been demonstrated that NO2, N2O4 and NO are the dominant gas phase products of the copper reactions in concentrated and dilute nitric acid, respectively [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
