The visitors showcased their superiority in a blistering first half performance, striking twice in a devastating spell after the half hour mark through Sanchez and Aaron Ramsey.
Ramsey then turned provider for Sanchez to put the game out of sight before half time, as the Chilean rounded Steve Harper to make it 24 goals in a stellar individual campaign.
Stephen Quinn grabbed a second half consolation for the Tigers but it was all Steve Bruce’s side could muster, and their top flight status hangs firmly in the balance with just three games remaining.
The void between the two sides was apparent almost immediately, and Harper had to be sharp to deny Sanchez’s fierce low drive.
Arsenal’s top scorer, many pundits’ choice for signing of the season, wasn’t to be denied for long though, as his free kick wrong footed Harper via a cruel deflection off Michael Turner.
Santi Cazorla was instrumental to the visitors’ stranglehold on the game, and his arrowed pass from deep just four minutes later found Ramsey, whose shot was also deflected past the helpless Harper – this time off Robbie Brady.
Arsenal’s third, just before half time, lacked even a trace of luck though as the two goalscorers were central again; Ramsey finding Sanchez brilliantly for the Chilean to unerringly round Harper and slide into an empty net.
The Gunners’ dominance faded after the break, and Hull were handed a lifeline when Quinn headed home Ahmed Elmohamady’s fine cross to grab his first goal of the season.
A dramatic comeback failed to materialise for the relegation strugglers who remain just one point and one place above the bottom three, while Arsenal were further buoyed by the return of Jack Wilshere as a late substitute after five months out.
The result means the Gunners are now nine points clear of fifth-placed Liverpool with a far superior goal difference, while they also moved level with Manchester City in the race to finish runners-up.