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NEET CHEMISTRYSolutionsMedium

Question

Which one of the following is incorrect for an ideal solution?

A

ΔHmix=0\Delta H_{\text{mix}} = 0

B

ΔUmix=0\Delta U_{\text{mix}} = 0

C

ΔP=Pobs−Pcalculated by Raoult’s law=0\Delta P = P_{\text{obs}} - P_{\text{calculated by Raoult's law}} = 0

D

ΔGmix=0\Delta G_{\text{mix}} = 0

Step-by-Step Solution

For an ideal solution:

  1. It obeys Raoult's law exactly over the entire range of concentration, so the observed pressure is equal to the calculated pressure, which means ΔP=0\Delta P = 0.
  2. The enthalpy of mixing is zero, ΔHmix=0\Delta H_{\text{mix}} = 0.
  3. The volume of mixing is zero, ΔVmix=0\Delta V_{\text{mix}} = 0.
  4. Since ΔH=ΔU+PΔV\Delta H = \Delta U + P\Delta V and both ΔHmix\Delta H_{\text{mix}} and ΔVmix\Delta V_{\text{mix}} are zero, the internal energy of mixing is also zero, ΔUmix=0\Delta U_{\text{mix}} = 0. However, mixing of miscible liquids is a spontaneous process. For any spontaneous process at constant temperature and pressure, the change in Gibbs free energy must be negative. Therefore, ΔGmix<0\Delta G_{\text{mix}} < 0. The statement ΔGmix=0\Delta G_{\text{mix}} = 0 is incorrect.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Solutions. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYSolutionsfollowingincorrectsolution

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