The visit of Unai Emery's men was seen as a potentially troublesome fixture, but the Reds made light work of them, with all of their revered front three finding the net in a devastating performance.
A chaotic five-minute spell in the first half saw Ainsley Maitland-Niles put Arsenal ahead, before a quickfire Firmino brace turned the score around. Sadio Mane and Mohamed Salah ensured a rampant Liverpool went into the break 4-1 up.
Liverpool's pressure did not subside after half-time and Firmino completed his treble from the spot 25 minutes from time, rounding off a miserable day for the Gunners and increasing the heat on Manchester City ahead of their meeting with Southampton on Sunday.
Arsenal went ahead in the 11th minute when Maitland-Niles tapped in Alex Iwobi's excellent left-wing cross.
But within five minutes, they were trailing.
Firmino equalised from close range after Stephan Lichtsteiner played a clearance against Shkodran Mustafi.
The Brazilian then brilliantly slalomed past two defenders and finished coolly into the bottom-right corner from 18 yards 90 seconds later.
Mane got in on the act just past the half-hour mark, emphatically slamming home after a squared pass from Salah.
The Egyptian scored their fourth on the stroke of half-time, converting a penalty after referee Michael Oliver adjudged he had been tripped by Sokratis Papastathopoulos.
Liverpool remained dominant after the interval, but Aaron Ramsey did go close to pulling one back – his shot deflecting away from the target, before an offside Pierre-Emerick Aubameyang comically put over from close range.
Firmino wrapped things up in the 65th minute, scoring from the spot after Sead Kolasinac appeared to nudge Dejan Lovren to the ground.
Liverpool flex their muscles ahead of City showdown
An away game against City comes up next for Liverpool, and this was certainly an impressive way to warm up for such an outing. With their front three in fine form, Klopp got the perfect collective performance to instil a bit of fear into Pep Guardiola's men.
Firmino the star
All three of Liverpool's frontline deserve honourable mentions, but Firmino was the standout for his link-up play, clever off-the-ball movement and three goals – the second of which being brilliant. A flawless display.
