what is the number of non-ionisable hydrogen in the compound formed upon hydrolysis of `PCl_5`

The final product obtained on hydrolysis of PCl_(5) is

The number of non-ionisable hydrogen atoms present in the final product obtained from the hydrolysis of PCl_5 is :

What is the ionisation potential of hydrogen atom?

PCl_(5) on hydrolysis gives

A certain compound 'A' has a molecular formula C_(5)H_(11)Br . It reacts with Mg metal in anhydrous ether to form compound B which upon hydrolysis gives n-pentane when compound A was reacted with Zn metal in dry ether gave 4.5 dimethyl octane. What is A B and draw their structures?