各物质浓度均为0.10 mol·dm-3的下列水溶液中,其pH值最小的是()。 A.NH4Cl B. NH3 C. CH3COOH D. CH3C...

作者: tihaiku 人气: - 评论: 0
问题 各物质浓度均为0.10 mol·dm-3的下列水溶液中,其pH值最小的是()。
选项 A.NH4Cl B. NH3 C. CH3COOH D. CH3COOH+CH3COONa
答案 C
解析 NH3为弱碱性,NH4Cl溶液为酸性,其Ka=Kw/Kb=5.6×10-5,可见Ka(CH3COOH)>Ka(NH4Cl),即酸性CH3COOH>NH4Cl。在CH3COOH中加入CH3COONa,根据同离子效应,CH3COONa中CH3COO-的存在抑制CH3COOH水解,因此酸性CH3COOH>CH3COOH+CH3COONa。

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