12.3. Chromatography
A subsection of Chemistry, 0620, through 12. Experimental techniques and chemical analysis
Listing 10 of 117 questions
Rose oil contains 2-phenylethanol. The structure of 2-phenylethanol is shown below. C C C C H C C H H H H H C H C H H O H On the structure above, draw a ring around the alcohol functional group. When heated with an alkali, 2-phenylethanol forms styrene. Styrene is an unsaturated compound. Describe a test for an unsaturated compound. test result Rose petals contain a variety of different coloured pigments. A student wants to identify these pigments. She grinds up rose petals with a solvent. Explain why. She then fi lters the solution through some glass wool. Suggest why she does not use fi lter paper. The student uses the apparatus shown below to identify the different pigments in the mixture. glass cover filter paper pure solvent State the name of this method of separating the pigments. On the diagram above, draw a spot, ●, to show where the mixture of pigments is placed at the start of the experiment. What is the purpose of the glass cover? The student also puts four spots of pure pigments, A, B, C and D, onto the fi lter paper. The diagram below shows the results of her experiment. pigments from rose petal A B C D Which of the pigments, A, B, C and D, are present in the rose petals? The solvent used in the experiment is ethanol. Draw the structure of a molecule of ethanol showing all atoms and bonds.
0620_w14_qp_21
THEORY
2014
Paper 2, Variant 1
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Rhubarb is a plant which has a red stem. A student separated the pigments in the rhubarb stem by chromatography. He used the apparatus shown below to extract the pigments. solvent A pieces of rhubarb State the name of the piece of apparatus labelled A. Suggest a suitable solvent, other than water, that he could use to extract the pigments. The solution of pigments was not concentrated enough to use for chromatography. Suggest how the student could make the solution more concentrated. The student carried out chromatography using the apparatus shown below. chromatography paper chromatography jar lid for chromatography jar solvent Y Z A spot of the pigment mixture was placed at Y. Explain why a spot of the mixture was not placed at Z. Describe how the rest of the procedure was carried out. Rhubarb leaves contain ethanedioic acid. The structure of ethanedioic acid is shown below. C C O O O O H H On the structure above, put a ring around a carboxylic acid group. Deduce the molecular formula of ethanedioic acid. A teacher heated ethanedioic acid with concentrated sulfuric acid. The equation for the reaction is: COOH COOHH2SO4 CO+ CO2+ X Deduce the formula of compound X. At the end of the reaction, the contents of the test-tube contained diluted sulfuric acid only. Explain why. Carbon dioxide is a product of this reaction. State one common source of the carbon dioxide in the atmosphere. Explain why an increase in the concentration of carbon dioxide in the atmosphere is harmful to the environment.
0620_w14_qp_23
THEORY
2014
Paper 2, Variant 3
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The list shows some of the compounds used to manufacture ink. calcium carbonate ethanoic acid iron(sulfate potassium dichromate(sodium sulfate sulfuric acid Which compound is present in limestone? Hydrated iron(sulfate is heated gently. FeSO4.7H2O FeSO4 + 7H2O Describe what you would see when a test-tube containing a small amount of hydratediron(sulfate is heated gently. Describe a test for aqueous iron(ions. test result Iron(sulfate can be prepared by reacting an excess of iron with dilute sulfuric acid. Complete the chemical equation for this reaction. Fe + H2SO4 FeSO4 + Describe how you could remove the excess iron from the mixture formed. Complete the structure of ethanoic acid to show all of the atoms and all of the bonds. C C O Give one observation when aqueous ethanoicacid reacts with magnesium. Black ink contains a mixture of different coloured dyes. Draw a labelled diagram of the apparatus used to separate these different coloured dyes by chromatography. Blue ink was placed at the bottom of a beaker containing water. After 2 days, a blue colour had spread throughout the beaker. at the start after 6 hours after 2 days water ink Explain these observations using the kinetic particle model.
0620_w17_qp_33
THEORY
2017
Paper 3, Variant 3
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Questions Discovered
117