11 mark
A group of students were investigating the purity of some water samples.
Their results are shown below:
| Boiling Point ( oC ) | |
| A | 103 |
| B | 105 |
| C | 101 |
| D | 102-106 |
Which sample is the purest?
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8.1 Purity, Formulations & Chromatography
2
1 mark
1 markA student carried out chromatography on a sample of green ink.
The distance moved by the solvent front is 5.8 cm.
The distance moved by the yellow dye is 4.5 cm.
Calculate the Rf value of the yellow dye to 2 significant figures.
0.78
0.80
1.3
26
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31 mark
A student was investigating the colours in black food colouring.
Chromatography was carried out on samples A-E and compared to the black food coloring.
The following chromatogram was produced.
Which of the following conclusions is not true for this chromatogram?
Sample B is insoluble in the solvent used
Samples C and D are pure substances
Sample D is the least soluble of the samples
The black ink is a mixture of A, E and an unknown
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41 mark
1 markParacetamol is a formulation.
One tablet has a mass of 1.30 g and contains 500 mg of the active ingredient, paracetamol.
What is the percentage by mass of paracetamol in one tablet?
4%
38%
50%
76%
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51 mark
A student set up the following apparatus to investigate the colours in three different food colourings.
What are the stationary and mobile phases for this experiment?
| Stationary | Mobile | |
| A | chromatography paper | water |
| B | beaker | start line |
| C | water | food colourings |
| D | start line | chromatography paper |
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