Using a commercial bait is a very effective way to kill black ants. Ants are attracted to the bait, which is a mixture of poison and a sweet substance. The ants eat some bait and bring some back to the nest, where the rest of the colony is also exposed to the poison. Over the course of one or two life cycles, the ants will be destroyed.  If you decide to use bait, be sure you take the precaution of making sure that there are no children or pets in the area. Commercial ant bait is available in hardware stores for about $4 per box. Follow the instructions on the packaging to get the bait traps ready, then place them on your countertops, in corners and in any other areas where you frequently see ants gather. If possible, place a trap in front of an ant trail. Different types of bait traps require different preparation. Some traps require you to place a few drops of bait on pieces of cardboard, then place the cardboard around your house. Other traps simply require peeling back a plastic wrapper and setting out the traps. Bait traps take a little longer to work than spraying and other methods of killing ants, but they are ultimately much more effective. Over the course of a few days, the ants will carry the bait back to their nest and poison the rest of the colony. In the meantime, make sure your house is clean of other food sources so that the ants eat the bait, not crumbs or sticky spots in your kitchen. If you want to make doubly sure the ants are gone for good, you can spray a pesticide as well. Purchase a store formula, mix up the contents based on the instructions, place the solution in a sprayer and spray the infested rooms. You may also apply the solution to the perimeter of your home to keep ants from coming inside.  Make sure that children and pets stay away from the sprayed areas, since they can become ill if they ingest the chemicals. You can also purchase an aerosol spray to apply directly on the black ants. These are usually indoor formulas that work well in areas like your kitchen. Apply the spray anywhere you see ants, and any cracks and/or crevices that you see them crawl into. This method usually leads to immediate death so sweep up any dead ants and dispose of them properly. If you spray in an area that children or pets may be in, be sure to adequately wipe down and clean the area so no one gets sick from the spray.
Buy commercial ant bait. Place the bait traps in the affected areas. Wait a few days for the traps to work. Try spraying with a pesticide.