The balanced chemical equation for the reaction between hydrogen and oxygen gases to form water is:2H g + O g 2HO g To determine the rate law expression, we need to know the reaction order with respect to each reactant. This information is typically obtained from experimental data. However, let's assume the reaction is first-order with respect to hydrogen H and second-order with respect to oxygen O . This is just an example, as the actual orders may vary depending on the specific reaction conditions.In this case, the rate law expression would be:rate = k[H]^1[O]^2where rate is the reaction rate, k is the rate constant, and [H] and [O] are the concentrations of hydrogen and oxygen, respectively.The overall order of the reaction is the sum of the individual orders:overall order = 1 for H + 2 for O = 3So, the overall order of the reaction in this example is 3. Keep in mind that the actual reaction orders may be different and need to be determined experimentally.