Carbon dioxide (co2) is used in industrial and research application, and is sometimes stored at very high pressure in rigid metal tanks. consider a tank with a volume of 0.8 m^3. (a) when the tank is first deliverd to a customer on a hot summer day, the pressure is measure to be 18,000 kpa at a temperature of 35 celsius. what the mass of co2 in the tank? (b) if the temperature remains constant, when enough co2 is used such that the tank pressure is reduced in half to 9,000 kpa, what is the mass of co2 in the tank?

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?