An insulated tank of volume \(2 \mathrm{~m}^{3}\) is divided into two equal chambers by a partition. One chamber contains an ideal gas of \(500 \mathrm{~K}\) and \(4 \mathrm{MPa}\), while the other is completely evacuated. Now, the partition is withdrawn and the gases are allowed to mix. Estimate the change in entropy of the gas.