hm...I'm not sure what NaC3H5O2 is, but when we had questions like these in CHem I, we know that it's a weak acid or base (since it's not a strong one).
SO if it is a weak base or acid, the Na dissociates with the C3H5O2, and they undergo fwd. and bckwd. Rx until reaching an equilibrium. Usually, you need a Ka or Kb to solve these kinda' things, so you can figure out the concentration of H3O+.
Then you can you the pH definition:
pH = -log([H3O+])