Alkyl halides and Alcohols Interconversions

Answers for Exercise:

Instead of PCl₅ other reagents have been used. Try to complete the equations.
If PCl₃ is used the side product is different( H₃PO₃ ). PCl₅ reactions are somewhat messy, it is usually difficult to separate the side products, a reagent that is toxic but gives product in high yield is Thionyl chloride ( SOCl₂ ). The side products in this case are both gases, therefore can be easily eliminated, they are SO₂ and HCl
PBr₃ reacts similar to PCl₃ , it can replace the -OH with -Br
Heating with NaOH is a useful method of replacing the halogen of an alkyl halide like ethyl bromide with -OH. Can HOH be used for the purpose? If not why not?