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<h2><span style="font-size:14.0pt;font-family:仿宋_GB2312;"> 1</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、原理</span></h2>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"><span> </span></span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">用标准浓度的酸溶液滴定水样，用酚酞和甲基橙做指示剂，根据指示剂颜色的变化判断终点。根据滴定水样所消耗的标准浓度的酸的用量，即可计算出水样的碱度。</span></p>
<h2 style="text-indent:28.0pt;"><span style="font-size:14.0pt;font-family:仿宋_GB2312;">2、仪器<span> </span></span></h2>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;font-family: 仿宋_GB2312">25mL</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">酸式滴定管、<span>250mL</span>锥形瓶。</span></p>
<h2 style="text-indent:28.0pt;"><span style="font-size:14.0pt;font-family:仿宋_GB2312;">3、试剂</span></h2>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> 1</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">．无二氧化碳水：配制试剂所用的蒸馏水或去离子水使用前煮沸<span>15min</span>，冷却至室温。<span> pH</span>值大于<span>6.0</span>，电导率小于<span> 2</span></span><span style="font-size:14.0pt;仿宋_GB2312">µ</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">S</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">／<span>cm</span>。</span></p>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> 2</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">．酚酞指示剂：称取<span>1g</span>酚酞溶于<span>100mL95</span>％乙醇中，用<span>O.1mol/LNaOH</span>溶液滴至出现淡红色为止。</span></p>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> 3</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">．甲基橙指示剂：称取<span>0.1g</span>甲基橙溶于<span>100mL</span>蒸馏水中。</span></p>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> 4</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">．碳酸钠标准溶液<span>(1</span>／<span>2Na2C03=0.0500mol/L)</span>：称取<span>2.648g</span><span>(</span>于<span>250</span>℃烘干<span>4h)</span>无水碳酸钠<span>(Na2C03)</span>，溶于无<span>CO2</span>的去离子水中，转移至<span>1000mL</span>容量瓶中，用水稀释至标线，摇匀。贮于聚乙烯瓶中，保存时间不要超过一周。</span></p>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> 5</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">．盐酸标准溶液<span>(0.0500mol/L)</span>：用刻度吸管吸取<span>4.2mL</span>浓<span>HCl(</span>ρ<span>=1.19g</span>／<span>mL)</span>，并用蒸馏水稀释至<span>1000mL</span>，此溶液浓度＝<span>O.050mol/L</span>。其准确浓度标定如下：</span></p>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> </span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">用<span>25.00mL</span>移液管吸取<span>Na2C03</span>标准溶液于<span>250mL</span>锥形瓶中，加无<span>C02</span>去离子水稀释至<span>100mL</span>加入<span>3</span>滴甲基橙指示剂，用<span>HCl</span>标准溶液滴定至由桔黄色刚变为桔红色，记录<span>HCl</span>标准溶液的用量<span>(</span>平行滴定三次<span>)</span>。按下式计算其推确浓度：</span></p>
<p><span style="font-size:14.0pt;font-family:仿宋_GB2312;">C=25.00</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">×<span>0.05/V</span></span></p>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> </span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">式中，<span> C</span>一盐酸溶液的浓度，<span> mol/L</span>；<span> V</span>一消耗的盐酸标准溶液体积，<span> mL</span>。</span></p>
<h2><span style="font-size:14.0pt;font-family:仿宋_GB2312;"> 4、步骤</span></h2>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> 1</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">．用<span>100mL</span>移液管吸取水样于<span>250mL</span>锥形瓶中，加入<span>4</span>滴酚酞指示剂，摇匀。若溶液无色，不需用<span>HCl</span>标准溶液滴定，请按步骤<span>2</span>进行。若加酚酞指示剂后溶液变为红色，用<span>HCl</span>标准溶液滴定至红色刚刚退为无色，记录<span>HCl</span>标准溶液的用量。</span></p>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> 2</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">．在上述锥形瓶中，滴入<span>1</span>—<span>2</span>滴甲基橙指示剂，摇匀。用<span>HCl</span>标准溶液滴定至溶液由桔黄色刚刚变为桔红色为止。记录<span>HCl</span>标准溶液用量<span>(</span>平行滴定三次<span>)</span>。</span></p>
<h2><span style="font-size:14.0pt;font-family:仿宋_GB2312;"> 5、计算</span></h2>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> 1</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">．总碱度</span></p>
<p><span style="font-size:14.0pt;仿宋_GB2312"> </span><span style="font-size:14.0pt;"> </span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">总碱度<span>(</span>以<span>CaO</span>计，<span>mg/L)= 
</span></span></p>
<p><span style="font-size:14.0pt;font-family:仿宋_GB2312;">总碱度<span>(</span>以<span>CaC03</span>计，<span>mg/L)= 
</span></span></p>
<p><span style="font-size:14.0pt;font-family:仿宋_GB2312;">式中：<span> C</span>一盐酸标准溶液的浓度，<span> mo1</span>／<span>L</span>：<span> P</span>一水样加酚酞指示剂滴定到红色退去盐酸标准溶液用量，<span> mL</span>；<span> M</span>一水样加酚酞指示剂滴定到红色退去后，接着加甲基橙滴定到变色时盐酸标推溶液用量，<span> mL</span>；<span> V</span>一水样体积，<span> mL</span>。</span></p>
<p style="text-indent:18.0pt;"><span style="font-family:仿宋_GB2312;font-size:14px;">2</span><span style="font-size:14px;">．根据<span style="font-size:14px;">T</span>、<span style="font-size:14px;"> P</span>之间的关系计算氢氧化物、碳酸盐、重碳酸盐碱度。</span></p>
