The Gunners returned to winning ways in the top-flight with a fine performance on the road. They were clinical up front with five of their six shots on target finding the back of the net.
Speaking after the game, Merson was impressed with the exceptional scoreline and said that it is a huge result for the north London giants.
He said via BBC Sport: "What a result. To go to Crystal Palace and score five goals and win it is a huge result."
Arsenal have moved within three points off leaders Liverpool with the victory over Palace, but the Reds have two games in hand at the moment.
The Gunners are playing catch-up in the title pursuit and they need to keep on winning games in order to pile the pressure on the table-toppers.