Chemical Analysis (8)

A pure substance is a single element or compound, not mixed with any other substance

A formulation is a mixture of compounds in measured quantities that has been designed as a useful product.

Formulations include fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods. E.g. alloys are mixtures of metals; they are harder than pure metals, so have a particular purpose.

A start line is drawn near the bottom of the paper. The mixture is spotted on the line.

A beaker is filled with small amount of solvent (it cannot touch or go above the start line when paper is placed in a beaker)

Paper is hung on a rod and placed in a beaker.

Solvent travels up the paper, thus separating the components.

Before solvent level reaches the end, the paper is taken out and the finish line is marked. The paper is dried.

The procedure works when different compounds have different affinities for the solvent/paper. Stronger attraction for the paper - travels slowly with the solvent etc.

Paper is called the stationary phase - it doesn’t move. Solvent is the mobile phase.

Distance moved by the spot / distance moved by solvent

It has a higher affinity for the solvent than for the paper.

Hydrogen – pop with burning splint over gas

Oxygen – glowing splint relights

Carbon dioxide – turns limewater (Ca(OH)2) milky

Chlorine – bleaches damp litmus paper and makes it white

Lithium compounds– crimson red flame

Sodium compounds - yellow flame

Potassium compounds - lilac flame

Calcium compounds – orange red flame

Copper compounds -green flame.