CH04-INS Experimental Operation: Mastering Titration Techniques | CH04-INS 实验操作：掌握滴定技术

📚 CH04-INS Experimental Operation: Mastering Titration Techniques | CH04-INS 实验操作：掌握滴定技术

The CH04-INS examination for International Chemistry A on 14 June 2023 focuses on practical titration skills, a core component of quantitative analysis in chemistry. This article provides a comprehensive guide to the experimental operation, from preparing standard solutions to calculating unknown concentrations, ensuring you are fully prepared for the practical assessment.

2023年6月14日的国际化学A CH04-INS考试重点考察滴定实验操作，这是化学定量分析的核心内容。本文全面指导您从配制标准溶液到计算未知浓度，确保您为实践评估做好充分准备。

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1. Introduction to the Titration Experiment | 滴定实验介绍

A titration is a volumetric technique used to determine the concentration of an unknown acid or base by neutralising it with a standard solution of known concentration.

滴定是一种容量分析技术，通过与已知浓度的标准溶液中和，来测定未知酸或碱的浓度。

The point at which the reaction is complete is called the equivalence point, detected using an indicator that changes colour at the end point.

反应完全的时刻称为等当点，通过指示剂在终点时变色来检测。

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2. Apparatus and Chemicals Required | 所需仪器与试剂

Essential apparatus includes a burette (50 cm³), pipette (25 cm³), conical flask, wash bottle, retort stand, white tile, and a pH meter or appropriate indicator.

必备仪器包括滴定管(50 cm³)、移液管(25 cm³)、锥形瓶、洗瓶、铁架台、白瓷板，以及pH计或合适的指示剂。

Chemicals required: standard solution (e.g., 0.100 mol dm⁻³ sodium hydroxide), unknown acid (e.g., hydrochloric acid), phenolphthalein or methyl orange indicator, and deionised water.

所需试剂：标准溶液(例如0.100 mol dm⁻³氢氧化钠)、未知酸(如盐酸)、酚酞或甲基橙指示剂、去离子水。

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3. Preparing a Standard Solution | 配制标准溶液

A standard solution is one whose concentration is accurately known. It can be prepared by dissolving a precisely weighed mass of a primary standard (e.g., anhydrous sodium carbonate) in deionised water and making up to a known volume in a volumetric flask.

标准溶液是浓度精确已知的溶液。可通过将精确称量的基准物质(如无水碳酸钠)溶解于去离子水中，并在容量瓶中定容至已知体积来配制。

The primary standard must be pure, stable in air, have a high molar mass to minimise weighing errors, and be soluble in water.

基准物质必须纯净、在空气中稳定、具有较高摩尔质量以减少称量误差，且可溶于水。

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4. Burette and Pipette Setup | 安装滴定管与移液管

Rinse the burette with the standard solution and then fill it, ensuring no air bubbles are trapped in the tip. Record the initial burette reading to ±0.05 cm³.

用标准溶液润洗滴定管，然后装液，确保尖嘴处无气泡。记录初始读数至±0.05 cm³。

Rinse the pipette with the unknown acid solution, then use a pipette filler to transfer exactly 25.0 cm³ into a clean conical flask. Do not blow out the last drop.

用未知酸溶液润洗移液管，然后使用洗耳球准确移取25.0 cm³至洁净的锥形瓶中。不要吹出最后一滴。

The burette should be clamped vertically, and a white tile placed under the flask to observe colour change clearly.

滴定管应垂直夹持，白瓷板置于锥形瓶下方，以便清晰观察颜色变化。

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5. Performing the Titration | 进行滴定

Add a few drops of indicator (e.g., phenolphthalein) to the conical flask. Swirl the flask while slowly opening the burette tap to add standard solution.

向锥形瓶中滴加几滴指示剂(如酚酞)。旋摇锥形瓶，同时缓慢打开滴定管活塞，加入标准溶液。

As the end point approaches, add the standard solution dropwise, swirling continuously, until a permanent colour change is observed.

接近终点时，逐滴加入标准溶液，持续旋摇，直到观察到永久性的颜色变化。

Repeat the titration until concordant results (titre volumes within 0.10 cm³ of each other) are obtained.

重复滴定，直到获得一致的结果(滴定体积相差在0.10 cm³以内)。

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6. Observing the End Point | 观察终点

With phenolphthalein in acid-base titrations, the colour changes from colourless to pale pink at the end point. A slight overtitration will produce a deep pink.

酚酞在酸碱滴定中，终点时颜色由无色变为浅粉色。轻微过量滴定会呈现深粉色。

For weak acid-strong base titrations, phenolphthalein is suitable; for strong acid-weak base, use methyl orange (yellow to red).

弱酸-强碱滴定适用酚酞；强酸-弱碱则使用甲基橙(黄变红)。

The end point should match the equivalence point as closely as possible to minimise indicator error.

终点应尽可能接近等当点，以减少指示剂误差。

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7. Recording and Processing Titration Data | 记录与处理滴定数据

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