Which of the following is correct for a solution of toluene and benzene? (1) $ H_{mix} = +ve$ (2) $ V_{mix} = -ve$ (3) $ S_{mix} = -ve$ (4) $ G_{mix} = -ve$See answer

Which of the following is correct for a solution of toluene and benzene 1 Hmix ve 2 Vmix ve 3 Smix ve 4 Gmix ve

Question

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Which of the following is correct for a solution of toluene and benzene? (1) $\\\Delta H_{mix} = +ve$ (2) $\\\Delta V_{mix} = -ve$ (3) $\\\Delta S_{mix} = -ve$ (4) $\\\Delta G_{mix} = -ve$

Basic Answer

Correct Answer:

(4) $Δ G_{mi x} = - v e$

Analyzing the Answer：

When toluene and benzene are mixed, an ideal solution is formed. In an ideal solution, the intermolecular forces between toluene and benzene molecules are similar to those between toluene-toluene and benzene-benzene molecules. Therefore, there is no significant heat change upon mixing, meaning the enthalpy of mixing ( $Δ H_{mi x}$ ) is approximately zero. The volume of the mixture is the sum of the volumes of the individual components, so the volume change upon mixing ( $Δ V_{mi x}$ ) is also approximately zero. However, mixing always increases the entropy ( $Δ S_{mi x}$ ) because the molecules become more disordered. Since $Δ G_{mi x} = Δ H_{mi x} - T Δ S_{mi x}$ , and $Δ S_{mi x}$ is positive, $Δ G_{mi x}$ will be negative, making the mixing process spontaneous.

Analysis of other options：

(1) $Δ H_{mi x} = + v e$ : Incorrect. For an ideal solution, the enthalpy of mixing is approximately zero, not positive. A positive enthalpy change would indicate that energy is required to mix the components.

(2) $Δ V_{mi x} = - v e$ : Incorrect. For an ideal solution, the volume change upon mixing is approximately zero. A negative volume change would imply a contraction in volume upon mixing.

(3) $Δ S_{mi x} = - v e$ : Incorrect. Mixing always leads to an increase in entropy (disorder) and thus a positive $Δ S_{mi x}$ . A negative entropy change would imply a decrease in disorder, which is not possible for a spontaneous mixing process.