醋酸钠-酚酞溶液受热变色因素的分析

Analysis on Factors Affecting Discoloration of Heated NaAc-Phenolphthalein Solution

醋酸钠-酚酞混合溶液受热变色实验,被诸多《无机化学实验》及《普通化学实验》教材采用,以说明升高温度对盐类水解的促进作用。该文采用分光光度计测定溶液吸光度的变化,研究其平衡的移动。结果发现,溶液随温度升高的明显色变,不仅由单纯水解平衡移动引起,更是由二氧化碳受热溢出使p H降低,乃至沸腾情况下醋酸的挥发等因素所致。

The color change experiment of heated Na Ac-phenolphthalein solution was widely adopted to explain the effect of hydrolysis equilibrium shifting with warming in many textbooks of the inorganic chemistry experiment and the general chemistry experiment.In this paper,spectrophotometer is used to determine the absorbance which can show the equilibrium shifting.It is found that the significant discoloration by neating did not only cause simple hydrolysis equilibrium movement,but affected by CO2 which will escape by heat to reduce p H and the volatilization of HAc under boiling conditions.