Benzene and naphthalene form an ideal solution at room temperature. The true statement for this solution are:
A. \(\Delta G\) is positive
B. \(\Delta S_{system}\) is positive
C. \(\Delta S_{surrounding} = 0\)
D. \(\Delta _{mix}H = 0\)
E. \(\Delta _{mix}V = 0\)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → B, C, D, E only
An ideal solution obeys Raoult’s law over the whole range of concentration. The A–B interactions are the same as the A–A and B–B interactions, so there is no heat change and no volume change on mixing. Mixing still increases the randomness, so it is spontaneous.
(A) ΔG is positive. — Incorrect. Mixing is spontaneous: ΔG = ΔH − TΔS = 0 − TΔS, which is negative.
(B) ΔSsystem is positive. — Correct. The molecules of benzene and naphthalene become randomly mixed, so the entropy of the system rises.
(C) ΔSsurrounding = 0. — Correct. No heat is exchanged with the surroundings: ΔSsurr = −ΔmixH/T = 0.
(D) ΔmixH = 0. — Correct. The intermolecular forces are the same before and after mixing.
(E) ΔmixV = 0. — Correct. The volume of the solution equals the sum of the volumes of the components.
NCERT (2026-27 edition):
Ideal Solutions
