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Questions 2.6g

Which apparatus and materials are required for chromatography? ----------
1. How many components are there in the black ink used? -------------------
2. What are their colors? ---------------------------------------------------------------
Why do some pigments deposit very near the point of application (baseline), while others deposit further away (That is, which property of substances does chromatography rely on)? -------------------------------------------------------------------
Chromatography helps us to achieve two main things. State them. ------------
Study the following chromatogram (used chromatography paper) then answer the questions that follow. P and Q are mixtures applied at points P and Q on the chromatography paper, held vertically in a jar or beaker. Baseline is the level of water (solvent) in a chromatography jar or beaker, which is covered. Solvent front is the level reached by water rising by capillarity in the chromatography paper.
1. Explain why the chromatography jar is normally covered.------------------------
2. How many components does Mixture P have? --------------------------
3. How many components does Mixture Q have? -----------------------------------
4. What can you say about R? ------------------------------------------------------------
5. Which two components are the same substance? --- Explain your answer ---
6. Which component is the least soluble? -------------------- Explain------------------
7. Which component is the most soluble? --------------------Explain. ---------------
A drop of Mixture Q (in question 5) is placed at the center of a chromatography paper held horizontally. A solvent is then added dropwise to Q, causing the latter to spread out in all directions on the paper. Draw and label a diagram to show the chromatogram that would result. ----------------------------------

Answers to Questions 2.6g

Chromatography jar, chromatography paper or filter paper, solvent, beaker, dropper and petri dish (if filter paper is used).
1. 3.
2. Yellow-orange, red, blue.
Some components are less soluble or adsorbed more by the chromatography paper; so they quickly deposit as solid matter as the solute spreads out and evaporates. Such components therefore deposit near the point of application. The most soluble and least adsorbed components deposit the farthest. Chromatography relies on differences in the solubility and adsorption of solutes (adsorption is the ability to be held on the surface of the paper).
Chromatography helps us to (a) separate dyes from a mixture (b) determine if a substance is pure or is a mixture.
1. To slow down evaporation of the solvent, so that it can rise higher and disperse the dyes better
2. 3.
3. 4
4. It is pure; that is, it consists of one substance, the sky-blue dye.
5. A and G.
6. A and G. They deposit near the baseline.
7. R. It deposits the farthest.
Dyes from plants rapidly fade, more so when washed with water, because it is soluble in water.