把0.02mol/LCH3COOH溶液和0.01mol/LNaOH溶液等体积混合,则混合溶液中微粒浓度关系正确的是(  )A. c(CH3COO-)>c(Na+)B. c(CH3COOH)>c(CH3COO-)C. c(H+)=c(CH3COO-)-c(CH3COOH)D. c(CH3COOH)+c(CH3COO-)=0.02mol/L

问题描述:

把0.02mol/LCH3COOH溶液和0.01mol/LNaOH溶液等体积混合,则混合溶液中微粒浓度关系正确的是(  )
A. c(CH3COO-)>c(Na+
B. c(CH3COOH)>c(CH3COO-
C. c(H+)=c(CH3COO-)-c(CH3COOH)
D. c(CH3COOH)+c(CH3COO-)=0.02mol/L

A、因混合后为0.05mol/LCH3COOH溶液和0.05mol/LCH3COONa溶液,该溶液显酸性,c(H+)>c(OH-),由电荷守恒关系可得c(H+)+c(Na+)=c(CH3COOH-)+c(OH-),则c(CH3COO-)>c(Na+),故A正确;
B、混合后为0.05mol/LCH3COOH溶液和0.05mol/LCH3COONa溶液,酸的电离大于盐的水解,则c(CH3COO-)>c(CH3COOH),故B错误;
C、由电荷守恒c(H+)+c(Na+)=c(CH3COOH-)+c(OH-),物料守恒关系c(CH3COOH)+c(CH3COO-)=2c(Na+),则2c(H+)=(CH3COO-)+2 c(OH-)-c(CH3COOH),故C错误;
D、因混合后为0.05mol/LCH3COOH溶液和0.05mol/LCH3COONa溶液,由物料守恒可知c(CH3COOH)+c(CH3COO-)=c(Na+)×2=0.01mol/L,故D错误;
故选A.
答案解析:0.02mol/LCH3COOH溶液和0.01mol/LNaOH溶液等体积混合,则实质上是0.05mol/LCH3COOH溶液和0.05mol/LCH3COONa溶液,该溶液显酸性,然后利用电荷守恒及物料守恒等来分析离子浓度的关系.
考试点:离子浓度大小的比较.
知识点:本题考查溶液中离子的浓度关系,明确混合后溶液的溶质是解答的关键,并注意一般酸与盐的混合溶液中溶液显酸性来解答即可,学会合理应用电荷守恒及物料守恒来解题.