Removing ceramic floor tile from concrete slab

electric chipping hammer. you don't have to patch too well, after all, it's going to be hidden by the new tile. you just want it reasonably flat. you may have to grind it down. ask at the tool rental place.

There are floor scrapers that are made for vinyl tile. Like a drywall knife. You need one like this only with a smaller blade. I have a digging bar that has a spade on one end and a bell on the other. Weights about 60 pounds. When removing tile I break out enough with the hammer to get the bar started then just slide it along the concrete until it hits the tile. You will have pieces all over so cover and plastic everything that you do not want to clean

Remember that the broken tile pieces are as sharp as glass. You well get tiny slivers that can bury themselves in hands,feet, knees etc.

I know this from bitter experience.

Your typical air compressor tool set usually has an air hammer tool with a chisel tip that will make short work of the ceramic tile with little damage to the floor.