Chromatography
Overview
How can you tell whether a coloured food dye is a single substance or a mixture, and what is in it? Chromatography spreads a mixture out across a piece of paper, separating its parts so each can be seen and identified. It is a simple idea with surprising power.
In this lesson you will learn how paper chromatography separates a mixture, why different substances travel different distances, how the Rf value gives each substance a measurable fingerprint, and how a locating agent reveals colourless spots.
Objectives
- Describe how paper chromatography is used to separate mixtures of soluble coloured substances, using a suitable solvent.
- Interpret simple chromatograms to identify: (a) unknown substances by comparison with known substances (b) pure and impure substances.
- [Supplement] Describe how paper chromatography is used to separate mixtures of soluble colourless substances, using a suitable solvent and a locating agent Knowledge of specific locating agents is not required.
- [Supplement] State and use the equation for R : f distance travelled by substance R = f distance travelled by solvent.
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Chromatography. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- In paper chromatography, the baseline should be drawn in: A. Ink B. Pencil C. Paint D. Chalk Answer: B
- A substance that is more soluble in the solvent will travel: A. Less far up the paper B. Further up the paper C. Sideways D. Not at all Answer: B
- The Rf value is the distance moved by the substance divided by the: A. Width of the paper B. Distance moved by the solvent front C. Time taken D. Mass of the substance Answer: B
- A substance moves 4 cm and the solvent front moves 8 cm. The Rf value is: A. 0.25 B. 0.5 C. 2 D. 4 Answer: B
- A locating agent is used to: A. Speed up the solvent B. Make colourless spots visible C. Colour the solvent D. Dry the paper Answer: B
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
Practice Mock Questions
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