Fetuli Talanoa crossed for three of the visitors' seven tries, as seventh-placed Widnes failed to score.
Jordan Abdull, Mahe Fonua, Stephen Michaels and Dean Hadley all also scored tries in a rampant Hull victory.
Vikings have now lost two consecutive games in the Super 8s, while Hull bounced back after their loss to Castleford on 5 August.
Talanoa and Fonua - who both returned to the side after injuries saw them miss that defeat - put Hull 22-0 up at half-time after Abdull's opening try.
Michaels and Hadley crossed after the break before Talanoa completed his hat-trick with 10 minutes remaining.
The result was wholly contrasting to Vikings' 46-6 win when the two sides last met at Widnes' home ground in March.
Media playback is not supported on this device
Hull FC coach Lee Radford: "I'm pleased with the scoreline and pleased with the zero - it's the first one of the season.
"We had good preparation and came here and did a very good job. We used the ball well and went over for some good tries."
Widnes Vikings coach Denis Betts: "They were better than us, simple as that.
"It's been a really tough couple of weeks. We've got lads out with injury and have gone out there on a short turnaround.
"I'm proud of the group but I'm disappointed we didn't show our talent and that is the disappointing thing."
Widnes: Mellor; Ah Van, Thompson, Chamberlain, Ince; Brown, Heremaia; Buchanan, White, Burke, Houston, Whitley, Cahill.
Replacements: Leuluai, Manuokafoa, Chapelow, Farrell.
Hull FC: Shaul; Michaels, Fonua, Yeaman, Talanoa; Tuimavave, Abdull; Taylor, Houghton, Watts, Minichiello, Manu, Ellis.
Replacements: Green, Hadley, Bowden, Pritchard.
Referee: Ben Thaler.
Leaders Hull FC comprehensively beat Widnes Vikings to go two points clear at the top of Super League.