When will the net enthalpy of formation of a solution (δhsolution) be endothermic?

Answer is: i t can be endothermic when the amount of energy needed to break the intermolecular forces in the solute is larger than the amount of energy given off by formation of intermolecular forces in the mixture, so solution must be heated.

In ideal solution the forces of attraction between the solute-solute and the solvent-solvent and solute-solvent molecules are the same.