Chelsea went ahead in the fourth minute when Reece James teed up Mount to curl a superb first-time effort into the top corner.
Leeds were reduced to 10 men on 24 minutes as Daniel James received a straight red card for a challenge on Mateo Kovacic, who limped off shortly after.
Chelsea doubled their advantage 10 minutes after the break through Christian Pulisic, who controlled Mount’s clever flick before drilling his strike into the bottom corner.
With seven minutes remaining, substitute Hakim Ziyech squared to Romelu Lukaku, who fired in for his third goal in two matches.
Chelsea now have 70 points, four more than fourth-placed Arsenal, although the Gunners have a match in hand.
Leeds are 18th on 34 points, inside the relegation zone on goal difference and having played a match more than both Burnley and Everton above them.