Dynamic Diagram of Component Concentration in Proton Balance Equation and pH Calculation of NaHCO3 Aqueous Solution
LIU Jian-Yu1, WANG Hai-Shui1**, LI Jing-Hong2
1. School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China; 2. Department of Chemistry, Tsinghua University, Beijing 100084, China
Abstract The proton balance equation of NaHCO3 aqueous solution is displayed as [H2CO3]+[H+]=[OH-]+[CO32-], and the relative content of the species including H2CO3, H+, OH-, and CO32- would be changed as the analytical concentration of NaHCO3 solution is varied. In this paper, the dynamic diagram of the concentration of each component in the proton balance equation with the solution concentration c is presented and plotted. From the dynamic diagram, the major, the minor, and the negligible species in the proton balance equation are directly and easily determined, thus, different pH formulas of solutions with different concentrations were obtained. The dynamic diagram can not only find new pH formulas, but also help students understand the physical meaning of the pH formulas correctly. It should be emphasized that the dynamic diagrams can provide new insights into the proton transfer reactions. For example,in concentrated solutions, the proton transfer reaction HCO3-+HCO3-⇌H2CO3+CO32- dominates. In 9.1×10-6 mol·L-1 solution, the proton transfer reaction H2O+HCO3-⇌H2CO3+OH- dominates.
LIU Jian-Yu, WANG Hai-Shui, LI Jing-Hong. Dynamic Diagram of Component Concentration in Proton Balance Equation and pH Calculation of NaHCO3 Aqueous Solution[J]. Chinese Journal of Chemical Education, 2024, 45(6): 108-112.
