用硝酸银溶液沉淀及分步沉淀卤素离子的数字化实验研究

Digital Experimental Study on Precipitation and Step-By-Step Precipitation of Halogen Ions by AgNO_(3) Solution

卤化银难溶电解质的沉淀溶解平衡是中学化学教学的重要知识点。应用本项目组研制的MXLab21先进数字化实验系统,结合银硫离子电极,测定AgNO_(3)溶液沉淀Cl~-,Br~-,I~-及其混合离子的沉淀曲线,即电动势(E)随AgNO_(3)溶液体积(V)变化的关系曲线。3种单一离子的沉淀曲线可以直观体现出滴定的电动势突跃范围与相应沉淀的溶度积大小的关系及其规律性变化。通过混合离子的沉淀曲线分析3种离子两两混合或3者混合时分步沉淀的可行性。Cl~-,Br~-,I~-的沉淀及分步沉淀的动态E-V曲线的建立,对中学化学教学具有重要作用,对化学学科核心素养的发展和培养具有重要价值。

The equilibrium of precipitation and dissolution of insoluble silver halide electrolyte is a key point in middle school chemistry teaching.The MXLab21 advanced digital experimental system developed by our project team cooperated with the silver-sulfur ion electrode to explore the precipitation curves of Cl-,Br-,I-and their mixed ions with AgNO_(3) solution as titrant.The precipitation curves presented the change of electromotive force(E)with AgNO_(3) solution volume(V).The precipitation curves of three kinds of single ions could directly reflect the relationship between titration E jump range and solubility product of the corresponding precipitation and the change rule of titration E jump range.Through the precipitation curves of mixed ions,the feasibility of step by step precipitation was explored in the case of the mixture of two or three ions.The establishment of dynamic E-V curves of the precipitation and step-by-step precipitation of Cl-,Br-,I-plays an important role in middle school chemistry teaching,and is of great value to the development and cultivation of the core quality of chemistry.