Chromatography and purity Quiz
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5 questions, one answer each
Each answer is checked as you go, with why.
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1. A pure substance is run in paper chromatography. How many spots does it give?
- A. None
- B. One
- C. Two
- D. Three
2. A spot moves 4.5 cm while the solvent front moves 9.0 cm. What is its Rf value?
- A. 2.0
- B. 4.5
- C. 0.50
- D. 0.20
3. What is the effect of impurities on the melting point of a solid?
- A. It lowers and widens the melting range
- B. It raises the melting point
- C. It makes no difference
- D. It makes it melt at an exact temperature
4. Why must the solvent front be marked as soon as the paper is removed?
- A. It dissolves the spots
- B. It makes the spots move faster
- C. It changes the colour of the spots
- D. It evaporates and its position would be lost
5. Two inks have the same Rf values. What can you conclude?
- A. They are certainly the same ink
- B. They are probably the same, but this does not prove it
- C. They are different inks
- D. They are pure substances