If all three win Chelsea take the automatic Champions League qualification spot, Arsenal finish fourth and have to play a qualifier and Tottenham are in the Europa League.
A Chelsea draw could still see them take the automatic spot if Arsenal do not better their result. However, if Chelsea draw 0-0 and Arsenal win 2-1 they will play off for third place as they would be on the same points and have the same goal difference and goals scored totals.
An Arsenal draw would see them finish fourth unless Spurs win.
Spurs need to win, and Arsenal fail to win, if they are to overtake their north London rivals as the Gunners have a far superior goal difference.