Page 38 - Curriculum Visions Dynamic Book

White phosphorus
Phosphorus is a highly reactive element and does not occur uncombined in nature. However, it is widely found in compounds in rocks, especially in light-coloured rocks called apatites (like calcium phosphate).
Three main forms of phosphorus are known: white, red and black phosphorus.
White phosphorus
Apatite, sand and carbon react at high temperatures to produce phosphorus and carbon monoxide gases and leave behind a slag of calcium silicate.
Phosphorus gas is collected by condensation and is made into a soft, white, waxy solid called white phosphorus.
One interesting property of white phosphorus is that it gives out a green glow that can easily be seen in the dark. This is caused by the reaction of phosphorus vapours with air.
White phosphorus can catch fire spontaneously in air and has to be stored under water. The main uses of white phosphorus are for incendiary (fire-starting) bombs, napalm bombs and rat poison.
In the past, white phosphorus was
also used for strike-anywhere matches,
also called “Lucifers”. White phosphorus is highly poisonous and many people working in the match- making industry used to suffer from “fossy jaw”, until safer forms of phosphorus were introduced (see next page). Modern strike-anywhere matches contain a phosphorus compound mixed with a source of oxygen, potassium chlorate. Striking them against a surface heats the mixture, which then reacts and ignites.
Phosphorus
 White phosphorus. The phosphorus molecule is highly reactive because the bond angle of 60° sets up great strains that can only be reduced by reaction.
EQUATION: Preparation of phosphorus from calcium phosophate
Calcium phosphate + carbon + silica ➪ phosphorus vapour + carbon monoxide gas + calcium silicate (slag)
Ca3(PO4)2(s) + 5C(s) + 3SiO2(s)
Preparing phosphorus
Phosphorus is prepared by heating crushed calcium phosphate
rock with coke and sand. This reduces the calcium phosphate to phosphorus.
The phosphorus vapour is then condensed and made into a liquid.
➪ P2(g) + 5CO(g) + 3CaSiO3(s)
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