Abstract A large number of bubbles generated in the demonstration experiment of Zn replacement of Fe in Fe2+ in junior high school chemistry textbooks interferes with students' cognitive learning of replacement reaction. The main reasons for this phenomenon are (1) the hydrogen evolution corrosion caused by the formation of Zn-Fe primary batteries after the replacement of Fe; (2) the hydrogen evolution potential of Fe is lower than that of Zn, so after Zn is displaced with Fe, the hydrogen evolution overpotential is reduced to produce a large number of bubbles. Based on this, the reaction conditions are controlled, the generation of bubbles in the reaction is inhibited, and the phenomenon of Zn displacing Fe is amplified. By adjusting the Fe2+ concentration and pH during the reaction to adjust the number of Zn-Fe primary cells and the hydrogen evolution overpotential, the conditions of this teaching demonstration experiment are explored. The results show that when the concentration of FeSO4 is 0.54 mol/L, pH=3.58, and the concentration of Fe3+ cannot be detected by KSCN, the Fe displaced by Zn can be observed to be attached to the surface of Zn and can be attracted by magnets, and the generation of bubbles cannot be observed.
JIANG Da-Chuan, DENG Yi-Chen, SU Lin, LI Sheng, ZHANG Yan-Hua, FU Jin-Song, LONG Du-Huo. Inquiry on Experimental Scheme of No Bubble Generation in Intermetallic Replacement Reaction Between Zn and FeSO4[J]. Chinese Journal of Chemical Education, 2023, 44(7): 105-108.
