IG Chem – Experimental Techniques (II) Purification Methods

An impure solid will have a higher melting point than a pure solid.

Pure water boils at 100°C, while salted water boils at about 102°C.

A liquid containing a dissolved solid will have a higher boiling point than the pure solvent.

Pure ice melts at 0°C, while ice with salt added to it melts at about -4°C.

Adding a solvent that the required solid is soluble in will not dissolve the solid.

Filter off the crystals, wash with a small amount of hot solvent and dry them to get the pure solid.

Purifying impure solids involves adding a solvent in which the required solid is insoluble.

The insoluble impurity that remains on the filter paper is called the filtrate.

A saturated solution contains the maximum amount of solute that can dissolve at a given temperature.

Simple distillation can be used to separate a liquid from a solution.

Fractional distillation is used to separate liquids with very different boiling points.

Desalination plants use fractional distillation to produce pure drinking water.

In simple distillation, the solvent is heated and turns into vapor, which is then condensed back into a liquid.

Fractional distillation can be used to separate ethanol from a fermentation mixture.

The fractionating column in fractional distillation increases the purity of the distilled product.