The Stamford Bridge clash between the Premier League title rivals was effectively over after 17 minutes with leaders Chelsea three goals to the good and the Gunners a man down.
Samuel Eto'o and Andre Schurrle had already scored before Eden Hazard saw his shot pushed away from goal by the hand of Alex Oxlade-Chamberlain.
Referee Andre Marriner awarded a spot-kick, but inexplicably brandished the red card in the face of a bemused Kieran Gibbs, before Hazard made no mistake from the spot.
Oscar scored either side of the interval before Mohamed Salah added a humiliating sixth to leave Arsenal back on the fringes of the title race, with Mourinho admitting his side's lightning start made the difference, although he still refuses to accept they are title favourites.
He told reporters: "'We had 10 amazing minutes and with that you can win the game and show everybody that you won't give a chance to any opponent.
"I was so happy with the approach, we came to kill and in 10 minutes we destroyed them.
"After that first 10 minutes, the job was easy. We pressed them high and well and attacked the space very quickly.
"We got the result with some numbers which are special for our fans, which makes it even more beautiful.
"Last Saturday (in the defeat at Aston Villa) the momentum was broken, and now we are trying to build more momentum.
"Man City have everything in their hands, Liverpool have everything in their hands.
"Nobody plays Champions League from the top four, they have just the Premier League matches to play and we have at least two big Champions League matches to play in between."
The one downside for Chelsea was the sight of Eto'o limping out of the action after nine minutes to be replaced by Fernando Torres, with Mourinho confirming the experienced striker is now facing a spell on the sidelines.
He added: "With his experience he thinks it's not big. Before the big tear, he was able to say enough is enough, but a hamstring is a hamstring."