The GATE Grind

GATE 2026 MT – Question 21

Metallurgical Thermodynamics · Solutions and chemical potential · 1 mark · Multiple choice

For a regular solution, which one of the following statements is correct? Here $\Delta H_{mix}$ is the enthalpy of mixing and $\Delta S_{mix}$ is the entropy of mixing.

  1. Both $\Delta H_{mix}$ and $\Delta S_{mix}$ are finite.
  2. $\Delta H_{mix}=0$ and $\Delta S_{mix}$ is finite.
  3. $\Delta H_{mix}$ is finite and $\Delta S_{mix}=0$.
  4. Both $\Delta H_{mix}$ and $\Delta S_{mix}$ are zero.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (A) Both $\Delta H_{mix}$ and $\Delta S_{mix}$ are finite.

Explanation

A regular solution retains the random configurational entropy of ideal mixing, $\Delta S_{mix}=-R\sum_i x_i\ln x_i$, but allows unlike-atom interactions to differ from like-atom interactions, giving a nonzero mixing enthalpy in general.

Thus the intended distinction is that both mixing quantities are finite, **A**. Zero mixing enthalpy is the ideal-solution special case.