浓硫酸与锌反应产生氢气的验证及原因探究

通过使用品红溶液、硫酸铜溶液及泡泡水等,可以验证浓硫酸与锌粒在加热条件下有氢气生成。提出产生氢气的原因与浓硫酸的自偶电离有关,并用多种金属进行验证。     

Acidity measurements at elevated temperatures. VII. Dissociation of water

The self-dissociation of water has been studied over the temperature range from 0 to 300°C and in KCl media from 0.02m to 2.7m. Also, isothermal pressure coefficients of the dissociation quotients have been obtained in these same media up to 250°C. A potentiometric method employing a hydrogen electrode concentration cell with flowing solutions was employed. The estimated accuracy of logQ _w values up to 250°C is 0.02 log units and at 300°C is 0.04 log units. Smoothing functions have been found which fit these data along with the precise potentiometric data of Harned and co-workers at low temperatures, the existing calorimetric data up to 55°C and the recent conductimetric measurements of pure water up to 271°C by Bignoldet al., within about 1.5 times the estimated errors. Thermodynamic quantities for the dissociation reaction have been tabulated for rounded values of temperature and ionic strength at the saturation pressure of water. The isothermal pressure coefficients of log Q_w varies approximately linearly with the square root of the ionic strength. This and the dependence of logK _w on the density of the water is consistent with the assumption that the molal volumes of aqueous ions vary linearly with the compressibility coefficient of water. The heat for the dissociation reaction at infinite dilution is also shown to be strongly dependent on density.     

二氧化碳缓冲溶液缓冲原理的数字化解析实验*

利用传感器数字化技术,分析室温下碳酸氢钠稀溶液直接吸收或释放二氧化碳气体的行为、pH及其变化趋势,设计数字化实验,为碳酸氢钠溶液在生物上作为二氧化碳缓冲液的行为提供化学实验验证。进行热力学计算,为其缓冲原理提供化学理论支撑。实验证明,碳酸氢钠稀溶液是构建二氧化碳缓冲液的充要条件,其作用原理是通过自偶电离建立碳酸氢钠碳酸钠缓冲对,从而与环境中的二氧化碳建立溶解平衡,其总方程式为:2HCO-3(aq)CO2-3(aq)+H2O(l)+CO2(g)。