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 $\Delta P = 0$.
2. The enthalpy of mixing is zero, $\Delta H_{\text{mix}} = 0$.
3. The volume of mixing is zero, $\Delta V_{\text{mix}} = 0$.
4. Since $\Delta H = \Delta U + P\Delta V$ and both $\Delta H_{\text{mix}}$ and $\Delta V_{\text{mix}}$ are zero, the internal energy of mixing is also zero, $\Delta U_{\text{mix}} = 0$. 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, $\Delta G_{\text{mix}} < 0$. The statement $\Delta G_{\text{mix}} = 0$ is incorrect.