The enthalapy of vaporization of water is given as  2257 KJ/kg. Consequently, enthalapy of condensation will be given as -2257 KJ/kg

During condensation, this much amount of energy would be released for complete condensation of water.

The given mass is 15 gm = 0.015 kg

Thus, the energy needed for condensation is 0.015 kg x -2257 KJ/kg = -33.855 KJ.

Thus, 33.855 KJ of energy would be released for condensation of 15 gm of water vapors.