The Chile international – who had scored in both of his previous games against the Tigers this season – was almost unplayable in a first-half blitz as the Gunners ripped apart a Hull side desperate for points to keep out of the relegation zone.
Sanchez scored twice in the first half, either side of Aaron Ramsey’s deflected strike before Steve Bruce’s men stemmed the flow with a header by Stephen Quinn in the second half.
The Gunners’ travelling fans staged a protest before the match about the ticket prices at the KC Stadium, with a banner asking: “£5 billion and what do we get? £64 a ticket”.
Yet by half-time they may have seen it as money well spent as Arsene Wenger’s side were a class apart and are now level on points with second-placed Manchester City with a game in hand.
The possession stats alone made uncomfortable reading for the Tigers, but for the first half-hour Hull had been happy to keep it tight and feed off any scraps, and certainly the visitors had been kept at arm’s length with only an inadvertent Tom Huddlestone back-flick towards his own goalkeeper threatening a goal.
Arsenal, however, began to put some snap into their passing, and following one exchange Sanchez skipped inside and pulled the trigger from 20 yards, but Steve Harper parried.
That was only putting off the inevitable and when Sanchez was chopped down by Jake Livermore in the 28th minute he took sweet revenge, smashing the free kick home with the aid of a flick off Michael Dawson’s head.
Hull’s precarious dam wall was breached and Arsenal poured through the gap.
Five minutes after the opening goal, Santi Cazorla’s stunning long pass picked out Ramsey, who turned and fired past Harper with aid of a heavy deflection off Robbie Brady’s leg.
Some breathtaking passing set up Mesut Ozil for a chance but his shot lacked venom, then the impressive Cazorla played in Sanchez who tried to lift the ball over Harper but the ’keeper stood his ground.
Sanchez was not to be denied a second, however, and in first-half stoppage time another Arsenal move lrft the Hull players like statues while Ramsey played in Sanchez who this time took the ball around 40-year-old Harper and scored into an empty net.
Hull trooped off dejected, having only an ambitious 40-yard effort by Dame N’Doye and a Sone Aluko header – which he tried to play back across goal – to show in their favour.
Bruce’s response was to send on Irish midfielder David Meyler for the ineffective Jake Livermore and the Tigers were instantly a tougher proposition.
It was Meyler who played a significant part as Hull pulled one back in the 56th minute. He clattered into Francis Coquelin and while Arsenal protested Ahmed Elmohamady played in a super cross that Quinn met with a stooping header than bounced past Ospina. Hull could really have been back in the game when McShane sent a bullet header over the crossbar but that let-off was all Arsenal needed and the Gunners were further buoyed when Jack Wilshere made his first return to action since an ankle operation in November, coming on for Ramsey.
Almost immediately he embarked on a mazy run past three Hull defenders, ended abruptly by Michael Dawson. Welcome back to the Premier League.
Sanchez, seeking his hat-trick, took the free kick but this time could not beat the wall.
Cazorla shot straight at Harper after a passage of play that left Hull simply bewildered, and then the same player was denied when the Tigers ’keeper saved with an outstretched leg.
Arsenal ended the match in total control with Hector Bellerin, Wilshere, Sanchez and Theo Walcott passing up chances to deliver the mercy blow.
Hull: Harper, Chester, Dawson, McShane, Elmohamady, Livermore (Meyler 46), Huddlestone, Quinn (Jelavic 81), Brady, N’Doye, Aluko (Robertson 65). Subs not used: McGregor, Rosenior, Bruce, Hernandez.
Arsenal: Ospina, Bellerin, Mertesacker, Koscielny, Monreal, Coquelin, Cazorla, Ramsey (Wilshere 68), Ozil, Sanchez, Giroud (Walcott 86). Subs not used: Szczesny, Gibbs, Gabriel, Rosicky, Flamini.