Three minutes later, the visitors went ahead when Torres fended off the challenge of Laurent Koscielny and volleyed home Mata's in-swinging free kick from eight yards.
Torres should have doubled his tally moments later, but the Spaniard lost his balance after rounding goalkeeper Vito Mannone.
Arsenal found an equaliser courtesy of a moment of magic three minutes before the break.
Gervinho collected Oxlade-Chamberlain's cut-back from the right, then cleverly turned inside the penalty area and unleashed a ferocious strike which flew into the top corner of Petr Cech's goal.
Chelsea were back in front within eight minutes of the restart, Mata's free kick ending up in the back of the hosts' net via a slight deflection off Koscielny.
Despite the Gunners applying heavy pressure on their opponents' goal, they were unable to salvage a point.
Cech produced two fabulous saves, including a world-class fingertip stop to deny Lukas Podolski.
Olivier Giroud missed a glorious chance in stoppage time, smashing into the side netting from close range.