01 Separation and Purification, MET

Sea water contains dissolved sodium chloride.

Which method is used to obtain pure water from sea water?

• chromatography

• distillation

• evaporation

• crystallisation

A mixture contains equal volumes of two liquids.

Liquid S has a boiling point of 80°C. Liquid T has a boiling point of 54°C.

The mixture is heated in the apparatus shown below.

What is X?

• 100% S

• 50% S and 50% T

• 10% S and 90% T

• 100% T

The diagram shows a chromatogram obtained from the colouring of three different sweets, X, Y and Z.

How many different red dyes are present in the sweets?

• 1

• 2

• 3

• 4

A mixture of coloured dyes is compared with other dyes using chromatography.

The chromatogram is shown above.

Which dyes are present in the mixture?

• 1 and 3

• 2 and 3

• 2 and 4

• 4 only

Hexane and water are immiscible liquids.

Which methods could be used to separate a mixture of hexane and water and how is the purity of separated hexane checked?

• method of separation : filtration

  purity check : find the boiling point

• method of separation : filtration

  purity check : obtain a chromatogram

• method of separation : use a separating funnel

  purity check : find the boiling point

• method of separation : use a separating funnel

  purity check : obtain a chromatogram

A liquid boils at a temperature of 100°C.

Which other property of the liquid proves that it is pure water?

• It does not leave a residue when boiled.

• It freezes at 0°C.

• It is neither acidic nor alkaline.

• It turns white anhydrous copper(II) sulfate blue.

The table shows the boiling points of some of the gases present in air.

argon -186°C

helium -269°C

neon -246°C

nitrogen -196°C

oxygen -183°C

When air is cooled to -200°C, some of these gases liquefy.

Which gases liquefy?

• argon, helium and neon

• argon, nitrogen and oxygen

• helium and neon only

• helium, neon and nitrogen

Methanol boils at 65°C and water boils at 100°C.

Methanol and water are completely miscible with each other.

Which method is used to separate a mixture of these two liquids?

• evaporation

• filtration

• fractional distillation

• paper chromatography

To separate a mixture of sand and salt the first step is to stir it in some water. What are the next two steps?

• crystallisation, then evaporation

• evaporation, then crystallisation

• evaporation, than filtration

• filtration, then crystallisation

Which method can be used to obtain copper(II) sulfate crystals from an aqueous solution?

• chromatography

• distillation

• evaporation

• crystallisation