We have calculated the probability of OH (OD) formation and energy deposit of the reaction exothermicity in the newly formed OH (OD), particularly in its vibrational motion, in the gas-surface reactions O(g) + H(ad)/Si --> OH(g) + Si and O(g) + D(ad)/Si --> OD(g) + Si. The reaction probabilities are about 0.10 at gas temperature 1500 K and surface temperature 300 K. The vibrational and translational motions of product OH share most of the reaction energy. Increasing the initial vibrational state of the adsorbate from the ground state to v = 1, 2, and 3 causes the vibrational energy of OH (OD) to rise nearly linearly, whereas the energies shared by other motions vary only slightly. The product vibrational excitation is strong in both OH and OD, leading to a population inversion. The amount of energy propagated into the bulk solid phase is about 13 % of the reaction energy in the O(g) + H(ad)/Si reaction, but the amount is significantly lower in O(g) + D(ad)/Si. The dependence of reaction probabilities and energy distributions on surface temperature is found to be weak, in the range of 0-600 K.