红樱桃化学化工论坛 » 【分析化学讨论版】 » 分析化学实验指导－16

yyx11 发表于 2007-3-24 11:00

分析化学实验指导－16

  <strong><font size="5"><font face="宋体">过氧化氢含量的测定(高锰酸钾法)<p /></font></font></strong><p class="MsoNormal" style="LINE-HEIGHT: 150%"><span><strong>实验目的：</strong><p /></span></p><p class="MsoNormal" style="TEXT-INDENT: 15.75pt; LINE-HEIGHT: 150%; TEXT-ALIGN: left; mso-pagination: widow-orphan; mso-char-indent-count: 1.5" align="left"><span style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">１．掌握</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">高锰酸钾法测定过氧化氢含量的原理和操作方法。</span><span lang="EN-US" style="COLOR: black; FONT-FAMILY: 宋体; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体"><p /></span></p><p class="MsoNormal" style="TEXT-INDENT: 21pt; LINE-HEIGHT: 150%; mso-char-indent-count: 2.0"><span style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">２．对</span><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">KMnO_４自身指示剂的特点有所体会。</span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang"><p /></span></p><p class="MsoNormal" style="LINE-HEIGHT: 150%"><b><span style="COLOR: black; LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">实验原理</span></b><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang"><p /></span></p><p class="MsoNormal" style="TEXT-INDENT: 21pt; LINE-HEIGHT: 150%"><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">H₂O₂分子中有一个过氧键—</span><span lang="EN-US" style="FONT-FAMILY: 宋体">O</span><span style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">—</span><span lang="EN-US" style="FONT-FAMILY: 宋体">O</span><span style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">—，在酸性溶液中它是一个强氧化剂<span lang="EN-US">,但遇</span></span><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">KMnO_４时为还原</span><span style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">剂。</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">在稀硫酸溶液中，过氧化氢在室温条件下能定量地还原高锰酸盐，因此，可用高锰酸钾法测定过氧化氢的含量。其反应如下：</span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang"><p /></span></p><p class="MsoNormal" style="LINE-HEIGHT: 150%; TEXT-ALIGN: center" align="center"><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">5H₂Ｏ₂ + 2MnO₄^— + 6H⁺ ＝ 2Mn²⁺ + 5O₂↑ + 8H₂O<p /></span></p><p class="MsoNormal" style="TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">开始反应速度慢，待<span lang="EN-US">Mn²⁺生成后，由于Mn²⁺的催化作用，加快了反应的速率,故能顺利地滴定到呈现稳定的微红色为终点。因而称为自动催化反应。稍过量的滴定剂(2×10^—6</span></span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang"> mo1·L^—1</span><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">)本身的紫红色即显示终点。<p /></span></p><p class="MsoNormal" style="LINE-HEIGHT: 150%"><b><span style="COLOR: black; LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">实验内容：<span lang="EN-US"><p /></span></span></b></p><p class="MsoNormal" style="TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">H₂O₂</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">含量的测定<span lang="EN-US"><p /></span></span></p><p class="MsoNormal" style="TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">用移液管吸取<span lang="EN-US">10mL3％</span></span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">H₂O₂</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">，置于<span lang="EN-US">250mL容量瓶中，加水稀至刻度，摇匀后，用移液管吸取25mL溶液置于250mL锥形瓶中，加 60mL水，加30mL3</span></span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang"> mo1·L^—1</span><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">H₂SO₄，用0.02</span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang"> mo1·L^—1</span><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">KMnO₄溶液滴定至微红色,30s内不消失即为终点。根据KMnO₄的浓度和消耗的体积，计算试样中</span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">H₂O₂</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">的含量。<span lang="EN-US"><p /></span></span></p><p class="MsoNormal" style="LINE-HEIGHT: 150%"><b><span style="COLOR: black; LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">注意事项</span></b><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang"><p /></span></p><p class="MsoNormal" style="TEXT-INDENT: 21pt; LINE-HEIGHT: 150%; mso-char-indent-count: 2.0"><span style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">若<span lang="EN-US">H₂O₂试样系工业产品，用上述方法测定误差较大，因产品中常加入少量乙酰苯胺等有机物质作稳定剂，此类有机物也消耗</span></span><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">KMnO_4。遇此情况可采用碘量法测定：利用</span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">H₂O₂和KI作用，析</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">出的<span lang="EN-US">I₂用Na₂S₂O₃溶液滴定：<p /></span></span></p><p class="MsoNormal" style="TEXT-INDENT: 21pt; LINE-HEIGHT: 150%; TEXT-ALIGN: center; mso-char-indent-count: 2.0" align="center"><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">H₂O₂ + 2H⁺ + ２I^— ＝ 2 H₂O +</span><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt"> I₂<span style="mso-spacerun: yes"> </span>E^0/</span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang"></span><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 6.5pt; mso-bidi-font-family: Batang">H₂O₂/ H₂O</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">＝１<span lang="EN-US">.77V</span></span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang"><p /></span></p><p class="MsoNormal" style="LINE-HEIGHT: 150%; TEXT-ALIGN: center" align="center"><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">S₂O₃^2— + I₂ ＝ S₄O₆^2— + 2I^—<p /></span></p><p class="MsoNormal" style="LAYOUT-GRID-MODE: char; LINE-HEIGHT: 150%"><b><span style="COLOR: black; LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">问题<span lang="EN-US"><p /></span></span></b></p><p class="MsoNormal" style="TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">１．用<span lang="EN-US">KMnＯ₄法测定</span></span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">H₂O₂</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">时，能否用<span lang="EN-US">HNＯ₃、HCl或ＨAc控制酸度? 为什么？<p /></span></span></p><p class="MsoNormal" style="TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt">2．</span><span lang="EN-US" style="FONT-FAMILY: 宋体; mso-bidi-font-family: Batang">H₂O₂有何用途。<p /></span></p><p class="MsoNormal" style="TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"><span lang="EN-US" style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt"><p></p></span></p><p class="MsoNormal" style="LAYOUT-GRID-MODE: char; LINE-HEIGHT: 150%"><b><span lang="EN-US" style="COLOR: black; LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体"><p></p></span></b></p>

wlgj168 发表于 2008-5-23 15:49

谢谢啦:lol :lol :handshake

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