Problem Analysis and Improvement of an Experiment on Reactivity of Metals in Chemistry I

摘要

In this study we investigated and tried to understand problems monitored in an experiment on reactivity of metals in chemistry I. Three problems were discussed. First, the reason that aluminium plate does not react with other metal ions such as zinc, iron and copper was studied and the way to overcome this problem was suggested. Second, the reason that the bubbles were generated when FeSO4(aq) and Zn(s) react was discussed. Third, the precipitates which appeared in the reaction of FeSO4(aq) and Zn(s) were identified. Through reference study and experimental investigation, we could reach the following results. First, aluminium could not react with other metal ions due to the surface oxide layer that is formed very fast and prevents aluminium from reacting with metal ions in solution. This problem could be overcome by allowing a competing reaction of acid and aluminium during the reaction of aluminium and metal ions. Second, the observed bubbles were identified to be hydrogen gas, produced by the reaction between metals and hydronium ion in the solution. Third, black precipitates that were produced on the surface of zinc plate and exhibited magnetic property were characterized to be Fe3O4(s), and brown precipitates that were produced in the solution phase were to be Fe2O3(s) by the analysis of X-ray photoelectron spectra.