Earlier, Tottenham failed to close the gap to Jurgen Klopp’s side as they suffered defeat by Wolves while third-placed Manchester City face Southampton on Sunday.
In a frantic opening, Ainsley Maitland-Niles registered his first goal for the Gunners on 11 minutes.
But a quick-fire Roberto Firmino double – the second featuring an excellent solo run – saw Liverpool go ahead just five minutes later.
Mohamed Salah then set up Sadio Mane for his side’s third before the Egypt international converted from the penalty spot in first-half stoppage time.
And Firmino completed his hat-trick with Liverpool’s second penalty of the match on 65 minutes after Sead Kolasinac was penalised for a foul on Dejan Lovren.
Klopp’s side are now unbeaten after 20 league games and will visit Manchester City in five days holding at least a seven-point advantage over their title rivals.
Arsenal remain fifth, after one win in four league games, two points adrift of the top-four.
