Abstract This paper investigated the reason for the difference between the amount of hydrochloric acid V1 consumed in the first step and the amount V2 consumed in the second step of the stepwise reaction between sodium carbonate and hydrochloric acid, which obtained using a self-constructed experimental setup and digital technology, by examining the pH curve. The experimental results indicated that the main reason for the difference between V1 and V2 was the effect of stirring speed, titration rate, solution concentration, and solution temperature on the pH sensor's lag response. Under conditions of sufficient stirring during the titration process, with faster titration rate, V1 was greater than V2 and the difference was larger. A higher concentration of sodium carbonate led to higher solution viscosity, exacerbating the lag response of the pH sensor. On the other hand, higher solution temperature decreased the solution viscosity, resulting in a smaller difference between V1 and V2. When the sodium carbonate concentration was low, the amount of sodium bicarbonate formed by the reaction between dissolved carbon dioxide in the water and sodium carbonate solution could not be neglected, and the purified water of the preparation solution was best used after boiling and cooling.
MENG Qing-Hua, LIU Mao-Zhen, XING Bei-Bei, LIU Cui. Exploration of pH Curve Errors in the Stepwise Reaction of Sodium Carbonate with Hydrochloric Acid[J]. Chinese Journal of Chemical Education, 2025, 46(3): 86-92.
