A 10 m3 oxygen tank is at 15 degree C and 800 kPa. The valve is opened and some oxygen is allowed to escape until the pressure in the tank drops to 600 kPa. The corresponding temperature is now 20 degree C. Calculate the mass in kg of oxygen that has been released from the tank. A team is designing a helium-filled balloon that will fly to an altitude of 7 km. As the balloon ascends, the upward force (buoyancy force) will need to exceed the total weight. Thus, the weight is critical. Estimate the weight (in newtons) of the helium inside the balloon. It is inflated at a site where the atmospheric pressure is .93 bar and the temperature is 23 degree C. When inflated prior to launch, the balloon is spherical (r=1.5 m) and the inflation pressure is the same as the local atmospheric pressure.