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一、知识要点梳理1.水的离子积常数水是一种极弱的电解质,它能微弱地电离生成H3O+和OH-:H2O+H2O(?)H3O++OH-(通常简写为H2O(?)H++OH-)。此电离平衡易受外界条件(温度、电解质等)影响,但遵循平衡移动原理,其中c(H+)·c(OH-)=Kw,Kw称为水的离子积常数,简称为水的离子积。由实验测知,在25℃时,1L纯水中只有1×10-7molH2O电离,所以,c(H+):c(OH-)=1×10-7mol·L-1,因此,在25℃时,Kw=c(H+)·c(OH-)=1x10-7×1×10-7=1×10-14。因水的电离是吸热的,所以当温度升高时,有利于水的电离.水的离子积增大。因此,Kw是一温度函数,只随温度升高而增大。如,100℃时,Kw=1×10-12;当温度恒定时,任何水溶液中的Kw均保持恒定。
First, the knowledge points Carding 1. Water ion product constant Water is a very weak electrolyte, it can be weakly ionized to generate H3O + and OH-: H2O + H2O (?) H3O++OH- (usually abbreviated as H2O (? ) H++OH-). This ionization balance is easily affected by external conditions (temperature, electrolyte, etc.), but follows the principle of equilibrium movement, where c(H+)·c(OH−)=Kw, Kw is called the ion product constant of water, and is simply called the ion product of water. . From the experiment, only 1×10-7 mol of H 2 O was ionized in 1 L of pure water at 25° C. Therefore, c(H+):c(OH-)=1×10 −7 mol·L −1, therefore, at 25° C. When Kw=c(H+).c(OH-)=1x10-7x1x10-7=1x10-14. Because the ionization of water is endothermic, when the temperature rises, it is beneficial to the ionization of water. The ion product of water increases. Therefore, Kw is a function of temperature and only increases with temperature. For example, at 100C, Kw = 1 x 10-12; when the temperature is constant, the Kw in any aqueous solution remains constant.