There seem to be a few suggestions that are missing the obvious. The range hood comes with a bracket to make it easier to install. It means you are not trying to hold up a 125 lb thing while trying to screw it to the wall. You can drill holes in the bracket where you need or want them. Mount it securely and the hood just hooks on.
I put a 120 lb 80" tv over my fireplace on a wall with NO studs. It is a SIP wall, 6-1/2" thick. I just ran bolts all the way through the wall and through a panel of 5/8" plywood slightly larger than the bracket. Long boots, washers and my own 250+ lbs can hang on that bracket.