The activation energy Ea for a reaction can be determined using the Arrhenius equation:k = A * e^-Ea / RT where k is the rate constant, A is the pre-exponential factor, R is the gas constant 8.314 J/mol K , T is the temperature in Kelvin, and e is the base of the natural logarithm.However, to calculate the activation energy for the reaction between hydrochloric acid HCl and sodium hydroxide NaOH , we need experimental data such as the rate constants at different temperatures or the reaction rate at different temperatures. Unfortunately, without this information, it is not possible to directly calculate the activation energy for this reaction.That being said, the reaction between HCl and NaOH is a well-known acid-base neutralization reaction:HCl aq + NaOH aq NaCl aq + H2O l This reaction is generally considered to have a low activation energy because it occurs rapidly and spontaneously at room temperature. The low activation energy is due to the strong electrostatic attraction between the positively charged hydrogen ions H+ from the acid and the negatively charged hydroxide ions OH- from the base, which readily combine to form water H2O .