Chemistry PYQ 26 of 152 · States of Matter

For two liquids A and B to form an ideal solution

  1. AEntropy of mixing must be zero
  2. BFree energy of mixing should be zero
  3. CEnthalpy of mixing should be zero
  4. DNone of the above

70th BPSC

Show answer and explanation

Correct answer: (c) Enthalpy of mixing should be zero

Explanation

An ideal solution obeys Raoult's Law, with A-A, B-B and A-B interactions nearly identical.

So no heat is absorbed or released: ΔH_mix = 0 (enthalpy of mixing is zero).

ΔS_mix > 0 and ΔG_mix < 0, so neither entropy nor free energy of mixing is zero.

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