The effect of non-magnetic impurity-scattering is considered on the asymmetric superconducting gap (SC) and the d-density wave (DDW) phase of the high Tc cuprates. The phase diagrams for the cuprates demonstrate that Tc decreases with scattering potential and is most affected in the coexisting phase of DDW and SC orders. Moreover, the SC gap to Tc ratio increases with doping and impurity scattering. The transition temperature of the DDW state, T∗ also decreases with scattering. The density of states in the mixed SC+DDW state for the underdoped (UD) phase, SC state in the overdoped phase and the DDW state in the UD phase, also suffers a modification. Its effect on specific heat results is also discussed. The increase in the gap to Tc ratio and the specific heat are also observed in the presence of the non-magnetic impurities. A suppression in the superfluid density is found with the increase in impurity.