Question

大学无机化学 求解。。。。。

http://zhidao.baidu.com/question/503622434.html?quesup2题目见连接

Answer 1

H3PO4 = H2PO4- + H+
K1= [H2PO4-]·[H+] / [H3PO4]
[H2PO4-] / [H3PO4] = K1 / [H+]
两边取负对数得：
-lg ( [H2PO4-] / [H3PO4] ) = -lg( K1 / [H+] )
-lg ( [H2PO4-] / [H3PO4] ) = pK1 - pH = 2.12 - 3.0 = - 0.88
即 lg ( [H2PO4-] / [H3PO4] ) = 0.88 ＞0
∴ [H2PO4-] ＞ [H3PO4] ··············· ①
同理可得：
lg ( [H2PO4-] / [HPO42-] ) = 4.2
∴ [H2PO4-] ＞ [HPO42-] ··············· ②
lg ( [HPO42-] / [PO43-] ) = 9.36
∴ [HPO42-] ＞ [PO43-] ················· ③
比较 ①、②、③ 可知，溶液中的主要存在型体为 H2PO4- （A）

Answer 2

H3PO4的pKa1、pKa2、pKa3分别为2.12、7.20、12.36，当H3PO4溶液的pH=3.0时，溶液中的主要存在型体为: B. H3PO4和H2PO4-

Answer 3

H3PO4的pKa1、pKa2、pKa3分别为2.12、7.20、12.36，当H3PO4溶液的pH=3.0时，溶液中的主要存在型体为: B. H3PO4和H2PO4-