They led 14-5 at half-time in Marcoussis thanks to tries by new cap Sharon Lynch and fly-half Tania Rosser.
Four more tries in the final quarter saw Ireland race clear to victory.
The first was a penalty try and then back rowers Siobhan Fleming and Lynch scored to make it three tries in a six-minute spell.
Winger Vikki McGinn added a late touchdown for Philip Doyle's side.
Ireland had rested most of the players after the win over New Zealand.
Both Donegal woman Larissa Muldoon and Nora Stapleton both played in today's win.
Ireland will play their semi-final on Wednesday.