Discuss the properties of phosphorus trichloride and phosphorus pentachloride.

Explanation

Properties of `PCl_3` : It is colourless oily liquid and hydrolyse in presence of moisture:
`PCl_(3) + 3H_(2)O to H_(3)PO_(3) + 3HCl`
It reacts with organic compounds containing -OH group such as `CH_(3)COOH_(3)C_(2)H_(5) -OH` etc.
`3CH_(3)COOH + PCl_(3) to 3CH_(3)COCl + H_(3)PO_(3)`
`3C_(2)H_(5)OH + PCl_(3) to 3C_(2)H_(5)Cl + H_(3)PO_(3)`
Properties of `PCl_5 : PCl_5` is a yellowish powder and in moist air, it hydrolyse to give `POCl_3` and finally gets converted to phosphoric acid
`PCl_(5) + H_(2)O to POCl_(3) + 2HCl`
`POCl_(3) + 3H_(2)O to H_(3)PO_(4) + 3HCl`
When heated, it sublimes but decomposes on strong heating
`PCl_(5) overset(Delta) to PCl_(3) + Cl_(2)`
It reacts with organic compounds containing -OH group converting them to chloro derivatives.
`C_(2)H_(5)OH + PCl_(5) to C_(2)H_(5)Cl + POCl_(3) + HCl`
`CH_(3)COOH + PCl_(5) to CH_(3)COCl + POCl_(3) + HCl`
Finely divided metals on heating with `PCl_5` gives corresponding chlorides:
`2Ag + PCl_(5) to 2AgCl + PCl_(3)`
`Sn + 2PCl_(5) to SnCl_(4) + 2PCl_(3)`