A20,000-liter storage tank was taken out of service to repair and reattach a feed line damaged in a collision with a tanker. the tank was drained and then opened several dayslater for a welder to enter and perform the required work. no one realized, however, that 5 liters of liquid n-nonane (c9h20) remained in a collection sump at the bottom of the tank after the draining had been completed. nonane has a lower explosive limit of 0.80 mole% and an upper explosive limit of 2.9 mole%8 (i. e., nonane-air mixtures at 1 atm can explode when exposed to a spark or flame if the nonane mole fraction is between the two given values). assume any liquid nonane that evaporates spreads uniformly throughout the tank. is it possible for the average gas-phase composition in the tank to be within the explosive limits at any time? even when the average composition falls outside those limits, why is an explosion still a possibility?