12. A few drops of liquid bromine were placed in the bottom of a gas jar as shown and left for several hours.

Bromine in gas jar

What two processes occurred in the gas jar during this time?

  • A.   evaporation and diffusion
  • B.   dissolving and evaporation
  • C.   condensation and diffusion
  • D.   dissolving and condensation
13. Which of the following statements is true?
  • A.   A mixture melts at a fixed temperature
  • B.   A compound melts over a range of temperatures
  • C.   A pure substance melts at a fixed temperature
  • D.   A pure substance melts over a range of temperatures
14. Which method could be used to separate a mixture of salt and water to obtain BOTH parts of the mixture?
  • A.   filtration
  • B.   evaporation
  • C.   distillation
  • D.   crystallization

Q15-16:
A student was investigating the dyes present in a food colouring using chromatography. He set up his chromatogram as shown in the diagram:

 

 chromatography experiment
15. Where should the student place the food colouring?
  • A.   At the top of the paper
  • B.   on the line
  • C.   Below the line
  • D.   In the solvent
16. Which statement about this experiment is correct?
  • A.   The line should be drawn in ink
  • B.   The solvent should be above the line
  • C.   The dyes must differ in their boiling point
  • D.   The dyes must differ in their solubilities in the solvent

17. A student obtained the following result from an unknown substance. He calculated the Rf value for the spot in order to identify it.

 

 chromatography experiment results
Which is correct for the calculation of the Rf value?
  • A.   Rf = c/a
  • B.   Rf = c/b
  • C.   Rf = d/a
  • D.   Rf = d/b

 Q18-20:
Several different methods are used to separate mixtures.
Select the best method to separate …...

  

18. ethanol from an aqueous ethanol solution.

  • A. filtration
  • B. fractional distillation
  • C. crystallization
  • D. chromatography

19. excess solid from the mixture formed by reacting excess solid copper(II)carbonate and dilute hydrochloric acid.

  • A. filtration
  • B. fractional distillation
  • C. crystallization
  • D. chromatography

20. solid copper(II)chloride from a copper(II)chloride solution.

  • A. filtration
  • B. fractional distillation
  • C. crystallization
  • D. chromatography