1 Separation and Purification Quiz 1

A mixture is separated by the set-up shown below. What is the mixture?

• Graphite and ethanol

• Oil and water

• Potassium chloride and water

• Sand and potassium chloride

The table shows the solubility of 4 substances, W, X, Y and Z, in ethanol and water.

Two methods of separation are given:

Method 1: add water to the mixture and filter 

Method 2: add ethanol to the mixture and filter

Which substances can be separated by both methods?

• W and X

•    W and Y

• X and Y

• Y and Z

Substance X has the following properties:

1.solid at room temperature and pressure 

2.high solubility in water 

3.decomposes and forms nitrogen dioxide when heated directly 

    Which method is most suitable in obtaining pure substance X from water?

• crystallisation

• evaporation to dryness

• fractional distillation

• sublimation

Both separation techniques are based in the large difference between melting and boiling points of the substances. 

• True

• False

Solids obtained through evaporation to dryness are always pure.

• True

• False

For crystallisation to occur, the solubility of the substance must be high at all solvent temperatures.

• True

• False