The midfielder scored the first and created the second, as the hosts moved to within two points of Stuart McCall's team.
County dominated the first half and deservedly took the lead in the 34th minute when Sproule latched on to Sam Morrow's pass to fire home a low shot from close range.
Sproule had earlier cleared the bar, while visiting keeper Darren Randolph denied Rocco Quinn shortly before the opening goal.
Motherwell's best chance of the first half arrived in the 41st minute when Shaun Hutchinson's close-range header flew over after he connected with Nicky Law's free-kick.
Both keepers made good saves early in the second half before County doubled their lead with 20 minutes remaining.
The lively Sproule provided the assist for Richard Brittain who found the bottom left-hand corner of the net from the edge of the box.
Morrow could have added a third on 75 but his header from seven yards flew wide of the left post.
However, the three points were duly sealed five minutes later as Iain Vigurs stroked home from 12 yards following Quinn's pass.