In acid-base reactions, the specific heat capacity of water, 4.18 J/gK, is typically used for calculations, especially when the solution is diluted. This value applies to aqueous solutions since water is the primary solvent. However, for concentrated solutions or different solvents, specific heat capacities may vary and should be determined accordingly. It's essential to consider the properties of the specific solution being used in the reaction. Accurate calculations depend on using the appropriate specific heat capacity for the conditions of the experiment.