Question: is nacn sn1 or sn2?
Answer: Nucleophiles like NaI, NaCN, KN3 etc. all have negative charges (I-, CN-, N3-) and so are at least decent nucleophiles, and will go SN2. Note that most of these compounds are basic. Nucleophiles like H2O or ROH aren't charged, and so are usually weak nucleophiles, and tend to go SN1.