In ideal solutions, the volume of the solution is the sum of the volumes of the components before mixing. Vsolvent +Vsolute =Vsolution i.e. there is no change in volume on mixing or ∆Vmix is zero. The intermolecular interactions between the components ( A−B interactions) are of same magnitude as the intermolecular interactions in pure components ( A−A and B−B interactions). Since, there is no change in magnitude of the intermolecular interactions in the two components present, the heat change on mixing, i.e. ∆Hmix in such solutions must be zero. H2O+CO2⟶H2CO3 This is a reaction in which carbonic acid is formed from water and CO2. So, this is not an ideal solution.