A 40.0-L container is divided into two equal parts by a rubber membrane. One half of the container has 1.50 moles of an ideal monatomic gas at 250 K, and the other half is a vacuum. The container does not allow any gas to escape but is free to exchange heat with the surroundings. The membrane breaks, the gas expands isothermally and eventually the gas reaches a new equilibrium condition occupying the entire volume. What is the change in entropy of the gas