The balanced equation for the reaction between calcium oxide and nitric acid is:

CaO(s) + 2HNO3(aq) → Ca(NO3)2(aq) + H2O(l)

In this equation, calcium oxide (CaO) reacts with nitric acid (HNO3) to form calcium nitrate [Ca(NO3)2] and water (H2O). The reaction involves a transfer of protons from the nitric acid to the calcium oxide, resulting in the formation of the salt calcium nitrate and the release of water molecules.