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在现行的几种中学化学课本中,对平衡常数的意义,都是这样叙述的:“平衡常数越大。表示化学反应达到平衡时生成物浓度对反应物浓度的比值越大,也就是反应进行得更完全些反应物的转化率也越大;反之,平衡常数越小表示反应进行的程度越小,反应物的转化率越小。”事实上,这种不加分析,简单的定论是不对的。例如,对于反应 N_2O_4(?)2NO_2,在 t=53℃,P=2大气压时,Kp=1.33.在 t=0℃,P=0.5大气压时,Kp=0.143,在这里虽然前一个温度下的 Kp 大于后一个温度下的 Kp;但是,前者在2大气压时的转化率却小于后者在0.5大气压的转化率。此外上述简单的观点也容易使人按照因果关系去推敲出:
In several current middle school chemistry textbooks, the meaning of the equilibrium constant is described as follows: “The larger the equilibrium constant, the higher the ratio of the product concentration to the reactant concentration when the chemical reaction reaches equilibrium, that is, the reaction proceeds The more complete the conversion rate of the reactants is greater; the other hand, the smaller the equilibrium constant indicates that the reaction is carried out to a lesser extent, the smaller the conversion rate of the reactants. ”In fact, this kind of analysis, simple conclusion is wrong of. For example, Kp = 1.33 for the reaction of N 2 O 4 (?) 2NO 2 at t = 53 ° C and P = 2 atm. Kp = 0.143 at t = 0 ° C and 0.5 atm, Kp is greater than Kp at the latter temperature; however, the conversion of the former at 2 atmospheres is less than that of the latter at 0.5 atm. In addition the above simple point of view is also easy to make people in accordance with the causal relationship to work out: