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次編輯
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滴定曲线
,無編輯摘要
{| class="https://image.baidu.com/search/detail?ct=503316480&z=0&ipn=d&word=%E6%BB%B4%E5%AE%9A%E6%9B%B2%E7%BA%BF&step_word=&hs=0&pn=112&spn=0&di=7146857200093233153&pi=0&rn=1&tn=baiduimagedetail&is=0%2C0&istype=0&ie=utf-8&oe=utf-8&in=&cl=2&lm=-1&st=undefined&cs=2617696106%2C3302115822&os=3480352390%2C2044506687&simid=2617696106%2C3302115822&adpicid=0&lpn=0&ln=776&fr=&fmq=1668229576849_R&fm=&ic=undefined&s=undefined&hd=undefined&latest=undefined©right=undefined&se=&sme=&tab=0&width=undefined&height=undefined&face=undefined&ist=&jit=&cg=&bdtype=0&oriquery=&objurl=https%3A%2F%2Fgimg2.baidu.com%2Fimage_search%2Fsrc%3Dhttp%3A%2F%2Fpic.baike.soso.com%2Fugc%2Fbaikepic2%2F9157%2F20160721164418-1758132686.jpg%2F300%26refer%3Dhttp%3A%2F%2Fpic.baike.soso.com%26app%3D2002%26size%3Df9999%2C10000%26q%3Da80%26n%3D0%26g%3D0n%26fmt%3Dauto%3Fsec%3D1670821603%26t%3D2d8ffda883079eededd9418327c7a94b&fromurl=ippr_z2C%24qAzdH3FAzdH3Fkwthj_z%26e3Bf5257_z%26e3Bv54AzdH3Fsj44wAzdH3Ffi5otggj6stgh_z%26e3Bip4%3Fptpsj%3D%25Bc%25CE%25Bm%25Ab%25C0%25FA%25CF%25DF&gsm=5a&rpstart=0&rpnum=0&islist=&querylist=&nojc=undefined&dyTabStr=MCwzLDIsNCw1LDEsNiw3LDgsOQ%3D%3D" style="float:right; margin: -10px 0px 10px 20px; text-align:left"|<center>'''滴定曲线'''<br><imgsrc="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic.baike.soso.com%2Fugc%2Fbaikepic2%2F9157%2F20160721164418-1758132686.jpg%2F300&refer=http%3A%2F%2Fpic.baike.soso.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1670821603&t=2d8ffda883079eededd9418327c7a94b " width="280"></center><small> 圖片來自百度</small> |}
一种表示滴定变化的图示
（见[[容量分析]]）过程中溶液性质。滴定曲线大致：①用浓度的[[对数函数]]表示（如图1和图2 中的pH和pZn，p即[[常用对数]]的负值）。由曲线等当点附近的变化，可以判定能否用[[指示剂]]确定终点，并据此选择合适的指示剂；用正比于浓度的某种性质表示，滴定曲线是两条直线，只是在[[等当点]]附近有些弯曲，由两直线（或其延长线）的交点确定终点。仪器分析方法确定终点大多是这种情况。
用氢氧化钠滴定盐酸时，在等当点附近，曲线几乎是垂直线，表示加入少量氢氧化纳时pH会发生很大的变化，称为[[滴定突跃]]。在等当点前0.1%到等当点后0.1%之间，溶液的pH由4.3变为9.7，相当于加入一滴氢氧化钠溶液能使 H的浓度改变几十万倍。pH突跃范围为4.3～9.7,此范围很大，包括从弱酸性到弱碱性区域。因此，在弱酸性范围内变色的指示剂（如[[甲基橙]]、[[甲基红]]）和在弱碱性范围内变色的指示剂（如[[酚酞]]）都适用。由于滴定曲线突跃大，终点变色敏锐。
{| class="https://image.baidu.com/search/detail?ct=503316480&z=0&ipn=d&word=%E6%BB%B4%E5%AE%9A%E6%9B%B2%E7%BA%BF&step_word=&hs=0&pn=358&spn=0&di=7146857200093233153&pi=0&rn=1&tn=baiduimagedetail&is=0%2C0&istype=0&ie=utf-8&oe=utf-8&in=&cl=2&lm=-1&st=undefined&cs=1625507967%2C3750845993&os=1273112802%2C1964760870&simid=3393730109%2C381050951&adpicid=0&lpn=0&ln=776&fr=&fmq=1668229756151_R&fm=&ic=undefined&s=undefined&hd=undefined&latest=undefined©right=undefined&se=&sme=&tab=0&width=undefined&height=undefined&face=undefined&ist=&jit=&cg=&bdtype=0&oriquery=&objurl=https%3A%2F%2Fgimg2.baidu.com%2Fimage_search%2Fsrc%3Dhttp%3A%2F%2Fyiqi-oss.oss-cn-hangzhou.aliyuncs.com%2Faliyun%2FUeditor%2FManage%2F20180602-8981828305b12642a1dd95.png%26refer%3Dhttp%3A%2F%2Fyiqi-oss.oss-cn-hangzhou.aliyuncs.com%26app%3D2002%26size%3Df9999%2C10000%26q%3Da80%26n%3D0%26g%3D0n%26fmt%3Dauto%3Fsec%3D1670822037%26t%3D069ae04f46123199b8396c62eb1b11f8&fromurl=ippr_z2C%24qAzdH3FAzdH3Fooo_z%26e3Bytqt_z%26e3Bv54AzdH3F1w5257AzdH3F1jpwts_99c_z%26e3Bip4s&gsm=14a&rpstart=0&rpnum=0&islist=&querylist=&nojc=undefined" style="float:right; margin: -10px 0px 10px 20px; text-align:left"|<center>'''滴定曲线'''<br><imgsrc="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fyiqi-oss.oss-cn-hangzhou.aliyuncs.com%2Faliyun%2FUeditor%2FManage%2F20180602-8981828305b12642a1dd95.png&refer=http%3A%2F%2Fyiqi-oss.oss-cn-hangzhou.aliyuncs.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1670822037&t=069ae04f46123199b8396c62eb1b11f8 " width="280"></center><small> 圖片來自百度</small> |}
乙酸为弱酸(pKa=4.76,Ka为离解常数)，其 pH突跃范围为7.7～9.7，只有两个pH单位，且处于弱碱性范围内，应选用在碱性范围内变色的指示剂，如酚酞。如果用甲基橙为指示剂，在滴定终点时，被中和的乙酸大约只有30%，且变色缓慢。