Scott Wood added 17 points with five 3-pointers while Purvis scored six during the run of 10 straight points midway through the second half that helped the Wolfpack (20-8, 9-6 Atlantic Coast Conference) pull away.
Freshman T.J. Warren scored 13 points, Lorenzo Brown had 11 and C.J. Leslie finished with 10 in an encouraging bounce-back performance for N.C. State, which is a half-game behind fourth-place Virginia in the race for one of the four first-round byes in the ACC tournament.
Lonnie Jackson scored 16 points and Olivier Hanlan and Ryan Anderson each had 12 for Boston College (12-16, 4-11).
The Eagles fell to 1-7 in conference road games and absorbed their second blowout on Tobacco Road in a four-day span. Duke beat them by 21 on Sunday.