作　　者： ; ;

机构地区： 华南理工大学化学与化工学院

出　　处： 《化学教育（中英文）》 2020年第4期21-25,共5页

摘　　要： 为推导出忽略二元弱酸H2A第二级离解的判据,设计了虚拟酸A和虚拟酸B并计算了酒石酸、虚拟酸A和虚拟酸B的准确氢离子浓度[H^+]T和近似氢离子浓度[H^+]AV。计算结果表明:忽略H2A第二级离解的判据与Ka1/Ka2比值相关。从极端二元酸(Ka1=Ka2)得到的判据为2Ka2/[H^+]AV≤0.11,其中[H^+]AV=1/2(-Ka1+√K2a1+4cKa1)。2 Ka2/[H^+]AV≤0.11判据具有广泛的普适性,可以用于所有二元弱酸溶液。新判据除了保证溶液氢离子浓度近似值[H^+]AV的准确度外(误差±5%以内),同时还具有覆盖浓度区间宽的显著优点。 It is difficult to give a clear and accurate criterion for ignoring the second dissociation process during the hydrogen ion concentration estimation for a weak diprotic acid,because the analytical concentration c,the dissociation constants of Ka1 and Ka2 will influenced this criterion in a very sophisticated manner.In order to solve this tough but important problem,an imaginary acid A,acid B and a special diprotic acid were designed and their properties were investigated.The results of this paper are as follows:1)The larger of[H^+]AV/2Ka2,the better of the approximate result,where the approximate value of[H^+]AV is given by[H^+]AV=-Ka1+√K2a1+4cKa1/2.2)The smaller of Ka1/Ka2 is,the more stringent criterion needs.3)The criterion for the special diprotic acid(Ka1/Ka2=1)is 2Ka2/[H^+]AV≤0.11,this rule can apply to all diprotic acids.4)The criterion of 2Ka2/[H^+]AV≤0.11 is powerful and robust,it can be widely used to make a right decision whether we ignore the second dissociation process or not.

关 键 词： 二元弱酸 氢离子浓度 近似计算 忽略二级离解 判据条件

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