Nilpotent elements in a ring

Let R be a commutative ring with 1. We say an element nR is nilpotent if there exists a number kN such that nk=0.

  1. Show that if n is nilpotent, then 1n is a unit.
  2. Give an example of a commutative ring with 1 that has no nonzero nilpotent elements, but is not an integral domain.