A student carries out an investigation on different plant extracts using paper chromatography. The experimental set-up he uses is shown below.
Where should he place the samples of plant extract?
On the pencil line
Below the pencil line in the solvent
Exactly 1 cm above the pencil line
Exactly 1 cm below the pencil line
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Paper chromatography was used to determine if a banned preservative, X, is present in four samples obtained from four different packaged foods labelled A, B, C and D.
The results of the analysis of the foodstuffs are shown in the diagram below.
Which foodstuff contains X?
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The diagram below illustrates the experimental set-up to carry out distillation. What are the correct labels for points A and B on the condenser?
| Point A | Point B |
A | water in | water in |
B | water in | water out |
C | water out | water in |
D | water out | water out |
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A student performs a technique using the apparatus shown.
Which separation technique has the student performed?
Crystallisation
Evaporation
Distillation
Filtration
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Rocksalt is the mineral form of sodium chloride. It is known to commonly contain sodium chloride and sand along with other trace impurities.
A combination of physical changes and separation techniques can be used to produce higher purity sodium chloride and sand.
What is the correct order of physical changes and separation techniques to separate sodium chloride and sand?
Melting, filtering, crystallising
Melting, filtering
Dissolving, filtering, crystallising
Dissolving, crystallising
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A substance was analysed and was found to have a boiling point of 450 °C.
At room temperature it is a soft grey solid.
Which temperature could be the melting point of a pure sample of the substance?
- 12 °C
56 °C to 72 °C
250 °C to 275 °C
142 °C
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Solid P melts at exactly 60oC and boils at exactly 310oC. Solid Q dissolves in ethanol and shows a green colour and a yellow colour when analysed using paper chromatography.
Which row is correct?
| Contains only one substance | Contains more than one substance |
A | Q | P |
B | Q | - |
C | - | Q |
D | P | Q |
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Pure H2O boils at 100 oC and freezes at 0 oC.
What is the melting point and boiling point of water after the addition of potassium chloride?
| Boiling point / oC | Freezing point / oC |
A | 103 | -3 |
B | 103 | 3 |
C | 97 | -3 |
D | 97 | No change |
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A student has performed an experiment which produced a precipitate. She correctly chooses to separate the precipitate using the process of filtration. She prepares the filter paper to be placed into the funnel by folding it as shown below.
Which diagram correctly illustrates the filter paper at stage 3?
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The diagram below shows the apparatus a student used to separate a product from a reaction mixture.
What did the mixture contain?
Aqueous sodium chloride and unreacted solid catalyst
Water and ethanol
Water and oil
Aqueous sodium chloride and oil
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A yellow solid, W is soluble in water. Which method of separation can be used to obtain the solid W from an aqueous solution?
Neutralisation
Chromatography
Distillation
Crystallisation
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Four different dyes labelled P, Q, R and S produced the chromatograms as shown below.
Which dye has an Rf value of 0.7?
S only
R only
Both P and Q
None
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A student has been given a sample of an amino acid to analyse by chromatography. As part of the investigation the student will have to use a locating agent to make the colourless amino acid spots visible. The Rf value is then calculated to identify the amino acid.
Which row describes the correct steps?
| How to add the locating agent | How to identify the amino acid |
A | Add to solvent | Calculate the Rf |
B | Spray on the chromatography paper before the experiment | Compare the Rf value to that of known solvents |
C | Spray on the surface of the solvent | Perform the experiment again and compare the Rf values |
D | Spray on the chromatogram | Compare the Rf value to that of known amino acids |
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It is important that substances used in the synthesis of medicines are pure as impurities in these products can be detrimental to our health. Samples of pure and impure paracetamol were analysed using chromatography. The resulting chromatogram is shown below.
The impure sample of paracetamol was contaminated with one of the raw chemicals used during its synthesis.
What is the Rf value of the chemical?
0.70
0.75
0.65
0.85
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A mixture of sugars can be separated out by paper chromatography.
The student sprays the dried chromatogram with a locating agent.
Why is this used?
To help the sugars dissolve in the solvent
To stop the sugars reacting with each other
To form coloured spots with the sugars
To aid the separation of the mixture
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