实验报告酸碱滴定

主题:pH指示剂滴定法PH 页:5(1352字) 发布时间:2012年11月4日
标题:酸碱滴定。

目标:
1.要使用滴定确定酸的浓度。2.技能的滴定技术。

仪器:
1.250年容量瓶
2. 10mL的量筒
3.25毫升的吸管
4. 50毫升滴定管
5. 250mL的烧杯
6.锥形瓶150毫升
7.待机Retord
8.白色瓷砖
9.秒表
10.移液器灯泡

化工:
1. HCl溶液
2.0.1 m氢氧化钠溶液
3. H2SO4溶液
4.蒸馏水
5.酚酞

介绍。
酸 - 碱滴定为酸或碱的浓度的恰好用酸中和或已知浓度的碱的酸/碱的确定。这允许一个未知的酸或碱溶液的浓度的定量分析。它利用的是酸和碱,以及如何,如果他们的公式是已知的酸和碱反应将知识之间发生中和反应。酸碱滴定,也可用于寻找化学品的纯度个百分点。当用弱碱弱酸反应,等当点的解决方案将是基本如果该碱是强和酸性如果酸更强。如果两者相等强度的,则等价pH将是中性的。然而,弱酸是不是经常滴定弱碱因为与指示器显示的颜色变化往往是快速的,因此很难观察者看到颜色的变化。在该指示器改变颜色的点被称为终点。一种合适的指示剂应选择,优选一个,将经历颜色变化(终点)靠近反应的等当点。首先,滴定管应与标准溶液,用未知溶液移液管,并用蒸馏水锥形瓶被冲洗。 Secondly, a known volume of the unknown concentration solution should be taken with the pipette and placed into the conical flask, along with a small amount of the indicator chosen. The known solution should then be allowed out of the burette, into the conical flask. At this stage we want a rough estimate of the amount of this solution it took to neutralize the unknown solution. The solution should be let out of the burette until the indicator changes colour and the value on the burette should be recorded. This is the first (or rough) titre and should be discluded from any calculations. At least three more titrations should be performed, this time more accurately, taking into account roughly where the end point will occur. The initial and final readings on the burette (prior to starting the titration and at the end point, respectively) should be recorded. Subtracting the initial volume from the final volume will yield the amount of titrant used to reach the endpoint. The end point is reached when the indicator just changes color permanently. This is best achieved by washing a hanging drop from the tip of the burette into the flask right at the end of the titration to achieve a drop that is smaller in volume than what can usually be achieved by just dripping solution off the burette. Acid–base titration is performed with a phenolphthalein indicator, when it is a strong acid – strong base titration, a bromthymol blue indicator in weak acid – weak base reactions, and a methyl orange indicator for strong acid – weak base reactions. If the base is off the scale, i.e. a pH of >13.5, and the acid has a pH >5.5, then an Alizarine yellow indicator may be used. On the other hand, if the acid is off the scale, i.e. a pH of <0.5, and the base has a pH <8.5, then a Thymol Blue indicator may be used.

指示器|颜色上偏酸性|颜色变化的范围基本面|色|甲基紫|黄色|0.0-1.6|紫色|
溴酚蓝|黄色|3.0-4.6|蓝色|
甲基橙|红|3.1〜4.4|黄色|
甲基红|红|4.4-6.3|黄色|
石蕊|红|5.0-8.0|蓝色|
溴百里酚蓝|黄色|6.0-7.6|蓝色| ...
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