what is the PH of a solution of .1 M NAN3 that disassociates into HN3

Answer 1

I don't necessarily agree with your description. NaN3 dissociates to Na^+ ad N3^-. The N3^- hydrolyzes in solution to HN3.
Can you write and balance the equation for the hydrolysis of the azide ion. Where do you get stuck from there?