It enables the Stags to climb back into the Blue Square Premier play-off places.
Mansfield Town had slipped out of the top five in midweek after Kettering's victory at Ebbsfleet.
But the Poppies' defeat at Stevenage, combined with the Stag's easy win, saw their positions reversed.
Mansfield's success was never in doubt once Jones opened his account and the Stags were coasting at 3-0 up by half-time.
David Holdsworth's men could only add one more in the second period through man of the match Jake Speight, but it was more than enough to send the fans home happy.
Keeper John Dandy – their oldest player at 22 – was City's star of the show and prevented Mansfield from notching even more.
The hosts started brightly and Shaun Kelly almost turned a Louis Briscoe cross into his own goal.
Moments later, Ollie Hotchkiss tried his luck from the edge of the box but was just too high.
Speight then got away down the left but his cross was just too high for Duffy.
A precise ball from Speight released Ryan Williams in the 13th minute only for Briscoe to head over the diminutive winger's centre at the far post.
Mansfield had a spell of pressure that began with a misplaced pass which saw Duffy's shot deflected wide off Kevin Roberts for a corner.
From it, Williams and Luke Jones twice had shots blocked, the last of which saw frantic Mansfield penalty claims for handball waved away by the referee.
As the Stags stepped up the pressure, Hotchkiss' deflected shot was well tipped over by John Danby.
From the corner kick, the Stags went in front as Williams' near post flick was headed firmly in from close range by a delighted Luke Jones.
Mansfield continued to press in search of a second and they got it from the same combination as the first in the 33rd minute.
This time Williams swung in a corner from the right and Luke Jones rose highest to head powerfully beyond Danby from 10 yards.
Yet another Williams corner enabled the Stags to make it 3-0. Danby pulled off a fine point blank save from Luke Foster's header but as the ball came out, the unfortunate Ben Jones turned the ball into his own goal in trying to tackle Speight.
Mansfield were by now rampant and Speight flashed wide of goal after cutting inside his marker on the edge of the box.
An intricate move involving Matt Somner and Speight saw the latter backheel for Duffy whose first time low shot was pushed around the post by Danby.
From the corner, Luke Jones was denied his hat-trick as his header was cleared off the line by Glenn Rule before Speight's overhead kick was into the arms of a grateful Danby.
As half-time approached, Speight was then crowded out with Chester rocking, but the visitors held out without a further concession.
Mansfield quickly reasserted their authority after the restart and Michael Lea did well to block a curling effort from Briscoe.
More good defending from Roberts then prevented Duffy heading in a Gary Silk centre.
On the hour mark, Williams whipped in a free-kick from the left for Duffy whose header was held by the diving Danby
With the Stags content to retain possession, the chances were not coming as quickly.
But Duffy was not too far away, the ball, appearing to strike his shoulder, from a 13th home corner of the game, taken by Williams.
With 13 minutes to go, Somner took a pass inside from Silk and had a dig from 20 yards, drilling inches wide of the left-hand post.
It was 4-0 to Mansfield soon after as Speight scored a much-deserved eighth of the season.
Armstrong fed Perry whose shot was blocked but the ball rebounded to Speight and he lashed in a superb strike that found the left hand corner from the edge of the area.
In the closing stages, Williams, from a tight angle, was denied by Danby, as Mansfield stayed in charge right until the final whistle.
MANSFIELD: Marriott, Silk, Foster, Jones, Armstrong, Briscoe, Somner, Hotchkiss, Williams, Duffy Speight.
Subs: Perry, Sandercombe, Sturrock, Challinor, Brough.
CHESTER: Danby, Roberts, Kelly, Rule, Lea, Wilkinson, Ellams, Davidson, Meynell, Jones, Coulter,
Subs: Murphy, Walker, Freeman, Maxwell.
Referee: Billy Khatib (Sunderland).