Question

Which of the following will be incorrect for ideal solutions?

• A. ${\Delta }_{mix}H=0$
• B. ${\Delta }_{mix}V\ne 0$
• C. Obeys Raoult’s law over the entire range of concentration
• D. The intermolecular attractive forces between thepure components A-A and B-B are nearly equal to those between the binary solution A-B

Answer 1

The correct option is B ${\Delta }_{mix}V\ne 0$

The solutions which obey Raoult’s law over the entire range of concentration are known as ideal solutions. The ideal solutions have two other important properties. The enthalpy of mixing of the pure components to form the solution is zero and the volume of mixing is also zero, i.e., ${\Delta }_{mix}H=0,{\Delta }_{mix}V=0$.
It means that no heat is absorbed or evolved when the components are mixed. Also, the volume of solution would be equal to the sum of volumes of the two components. At molecular level, ideal behaviour of the solutions can be explained by considering two components A and B. In pure components, the intermolecular attractive interactions will be of types A-A and B-B, whereas in the binary solutions in addition to these two interactions, A-B type of interactions will also be present. If the intermolecular attractive forces between the A-A and B-B are nearly equal to those between A-B, this leads to the formation of ideal solution.