Question

In the reaction of phosphorus with chlorine to form a phosphorus chloride, whether PCl3 or PCl5 forms depends on

1) whether the reaction is carried out in the gas phase or in solution.

2) the amount of chlorine present.

3) whether the chlorine used is molecular or atomic.

4) the amount of moisture present.

5) which allotropic form of phosphorus is used

Answer 1

Answer: 1) whether the reaction is carried out in the gas phase or in solution.

Phosphorus trichloride, PCl3, is prepared by the action of chlorine on white or red phosphorus on heating in a retort, and condensing the phosphorus trichloride vapour in a cooled dry receiver.

2P + 3Cl2 = 2 PCl3

Phosphorus pentachloride, PCl5 is prepared by passing chlorine into a well cooled solution of phosphorus in carbondisulphide and crystallizing out the product formed.

2P + 5Cl2 = 2 PCl5