C1.3 PRINCIPLES OF CHEMISTRY

Question 1

The start line, or baseline, in chromatography should be drawn in pencil. Explain why.

Answer 1

A baseline drawn in pencil will not dissolve in the solvent.

Question 2

In a chromatography experiment, why must the solvent level in the beaker be below the baseline?

Answer 2

If the solvent were above the baseline, the substances would just dissolve and form a solution in the beaker.

Question 3

In a chromatography experiment to compare the dyes in two different inks, one of the ink does not move at all from the baseline. Suggest a reason for this.

Answer 3

The dye may be insoluble in the solvent.

Question 4

What is a solvent?

Answer 4

A solvent is a liquid that will dissolve a substance ( solute ).

Question 5

What does the term soluble mean?

Answer 5

If a substance is soluble in a solvent it DISSOLVES in that solvent.

Question 6

What method would you use to separate a pure liquid from a solution of a solid and the liquid?

Answer 6

Distillation

Question 7

To separate two liquids by fractional distillation they must have different …

Answer 7

Boiling points

Question 8

Process to be used to separate liquid contaminated with other liquid

Answer 8

Fractional Distillation

the mixture boiled.

liquid with the LOWEST BOILING POINT turns to a vapour first, rises up to the fractionating column and is condensed back to liquid in the condenser.

the next lowest boiling point liquid comes off, and so on until all the liquids have separated.

Question 9

Process to be used to separate liquid contaminated with soluble solids dissolved in them

Answer 9

Distillation

The solution is heated, the solvent boils and turn into a vapour. it is condensed back to pure liquid and collected.