An insulated tank of volume \(2 \mathrm{~m}^{3}\) is divided into two equal compartments by a thin and rigid partition. One compartment contains an ideal gas at \(400 \mathrm{~K}\) and \(300 \mathrm{kPa}\), while the other is completely evacuated. Now, the partition is suddenly removed and the gases are allowed to mix. The equilibrium is reestablished by equalizing the pressure and the temperature. Estimate the change in entropy of the gas.