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Chromatography

  1. [2011 OL] [2008 OL]

A solution of dye can be separated into its constituent colours using the method shown in the diagram.

Study the diagram and answer the following questions.



  1. What name is given to this type of separation?

  2. Name a suitable solvent for this investigation

  3. What would you expect to notice on the piece of chromatography paper after some time?

  4. The ink spot is placed on the chromatography paper just above the level of the solvent.

Why?


  1. [2008]

    1. Describe an experiment to investigate the composition of inks in markers containing water-soluble inks, to see if they are a single-colour ink or a mixture of coloured inks.

    2. On completion of the experiment how is it possible to distinguish between a marker containing a pure single-colour ink and a marker containing mixture of coloured inks.



  1. [2006]

A spot of water-soluble ink was put on a piece of chromatography paper and set up as shown in the diagram. The ink used was a mixture of different coloured dyes.

    1. What happens to the ink spot as the water moves up the paper?

    2. What would happen to a spot of water-soluble ink consisting of a single coloured dye if it were used in the above experiment?






  1. Paper chromatography was used to find the composition of brown ink in a pen.
    The same liquid, paper and pen were used in each of the three experiments shown.
    They were started at different times, C first then B and finally A.




  1. Why is the ink dot above the level of the liquid in each beaker?

  2. What caused the dots of ink on the papers B and C to spread upwards?

  3. Why were colours, other than brown, seen in B and C as the ink moved up the paper?



  1. [2011 OL]

Separation techniques are very important in chemistry.

A group of students carried out an experiment to separate salt from rock salt (impure salt containing sand and clay).



A number of the pieces of equipment they used are shown below.


Answer the following questions on this experiment.



  1. Which of the pieces of equipment A, B, C or D was used to grind up (crush) the rock salt at the beginning of the experiment?

The rock salt was placed in a container and hot water added.



The mixture was added to allow the salt to dissolve.

  1. Name the piece of equipment (container) in which the crushed rock salt was placed before the hot water was added.

  2. Name the piece of equipment that was used to heat the water.


The salt and water was separated from the insoluble impurities (dirt) using the apparatus shown on the right.

  1. What name is given to the separation technique?




  1. The salt and water was collected at X.
    Explain why the insoluble impurities (dirt) were held at Y.



  2. To get the salt from the mixture of salt and water the water was removed.

This could be done be either evaporation or distillation.

The apparatus used for these techniques is drawn below.



Identify each technique.




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