Analysis on Factors Affecting Discoloration of Heated NaAc-Phenolphthalein Solution

The color change experiment of heated NaAc-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 pH and the volatilization of HAc under boiling conditions.