Formation of a solution from two components can be considered as
$(i)$ Pure solvent $\to$ separated solvent molecules $\Delta H_1$
$(ii)$ Pure solute $\to$ separated solute molecules $\Delta H_2$
$(iii)$ Separated solvent and solute molecules $\to$ solution $\Delta H_3$
Solution so formed will be ideal if

• A
  $\Delta H_{soln} = \Delta H_3 - \Delta H_1 - \Delta H_2$
• B
  $\Delta H_{soln} = \Delta H_1 + \Delta H_2 + \Delta H_3$
• C
  $\Delta H_{soln} = \Delta H_1 + \Delta H_2 - \Delta H_3$
• D
  $\Delta H_{soln} = \Delta H_1 - \Delta H_2 - \Delta H_3$