11. If the U. S. government had allowed helium to be exported, how many moles of helium would have been needed to fill the Hindenberg? How much weight could the ship then have lifted, using He instead of ?

12. Why are and He the only two gases that can be used in lighter-than-air craft?

13. If the gas bags were filled on a hot day, at 30, by what percent would they have shrunk if the temperature fell to 15?

14. If , , and all behave as ideal gases, would the lifting ratio of a balloon (the number of times the weight of gas it can lift) change as the temperature changed? Why, or why not?

15. When 1 g of unknown liquid is vaporized at 80 and 1.01 atm pressure, it occupies a volume of 0.622 liter. How many moles of the liquid are present?

16. What is the molecular weight of the liquid of Problem 15?

17. If the molecules of the liquid in Problem 15 are 34.7% oxygen by weight, and contain only carbon, hydrogen, and oxygen, what might the liquid be? (We have encountered it previously in this problem set.)