Quoted from Langless28:If there is only one outlet on a 20 amp breaker, the outlet must be rated for 20 amps per NEC. We are allowed to use 15 amp outlets on a 20 amp branch circuit because the notion that your never only going to use one outlet.
I'm a electrician...and I can say that this is not true. Your breaker must be sized according to the device with the lowest amperage rating. A easy way to tell if you have a 20 amp plug is to see if it the hot and neutral only run vertically, a 20 amp plug has a vertical and horizontal slot.