Question

Alkyl halide giving SN1 or SN2 rxn

Answer 1

Yes alkyl halides do give Sn1 and Sn2 reactions.

Regards,
Adithiya

Answer 2

The SN2 reaction is concerted. That is, the SN2 occurs in one step, and both the nucleophile and substrate are involved in the rate determining step. Therefore the rate is dependent on both the concentration of substrate and that of the nucleophile.
The SN1 reaction proceeds stepwise. The leaving group first leaves, whereupon a carbocation forms that is attacked by the nucleophile.