把50ml0.1mol/L的CH3COOH溶液和50ml0.05mol/LNaOH溶液混合,
混合后溶液：n(CH3COOH)=n(CH3COONa)=2.5 m mol (2.5*10^-3mol)
显然是缓冲溶液:
CH3COOH CH3COO- +H+
Ka=[H+]*[CH3COO-]/[CH3COOH]
=约=[H+]*c(CH3COO-)/c(CH3COOH)
=[H+]*n(CH3COO-)/n(CH3COOH)
==[H+]
因此[H+]=2*10^-5
pH=-lg[H+]=-lg2*10^-5=4.7
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[H+] 代表平衡浓度
c(CH3COO-)代表起始浓度为什么[H+]*n(CH3COO-)/n(CH3COOH)=[H+]为什么n(CH3COO-)=n(CH3COOH)因为醋酸的物质的量是氢氧化钠的2倍