Need help with problems 15-22 & 24-26

15. When 0.560g of N2(g) was cooled to 40C, the pressure of the gas was 66.7kPa. What was the volume of the container holding the gas? Ans: 0.581L 16. At standard pressure and 27C a gas mixtare has a volume of 42.0L. What is the namber of gas particles present? Ans: 1.03E24 17. Calculate the density of methane gas, CH4, under each of the following conditions: a) STP b) 950 tor and 0C c) 400mm and 23C Ans: a) 0.7142g/L b) 0.8928gL c) 0.4105g/L 18. The best vacuum that can be attained presently is about 1E14kPa at 0C. Under these conditions, how many molecules will be contained in a volame of 1.0mL ? Ans: 2652 molecules 19. Calculate the mass of cne molecule of gas if 20.4g occupy 11.4L at 507kPa and 273C. Ans: 2.66E23g 20. An empty steel gas tank with valve has a mass of 56.7kg and a capacity of 42.5L. When the tank was filled with oxygen gas to 13.79MPa at 25C, what percent of the total mass of the full tank was oxygen? Assume the validity of the ideal gas law. Ans: 11.8% 21. A gas is stored in a 50L tank at 20atm and 17C. a) How many moles of gas are in the tank? Assume ideal behaviour. b) If the tank weighs 10.505kg empty and 10.673kg when filled with a gas, caiculate the molar mass of the gas. Ans: a) 42 moles b) 4g/mol Avogadro's Hypothesis wed Feb 14 Content 22. A sample balb contains 0.712g of H2(8) at a certain temperature and pressure. Under the same conditions the bulb can hold 13.0g of an unknown gas. What is the molar mass of the unknown gas? Ans: 36.5g/mol 23. A gas has an empirical formila CH2. A bulb is filled with the gas at 50C and 1013kPa and its mass determined. The bulb is then emptied and refilled with O2 ) tat the same temperafure and pressare. The mass of the gas is 1.75 times as much as the mass of the O2. Determine the moleculat formula of the gas. 7n0t im 0 or tront Ans: C4H8 Partial Pressures wec Feb ft (ontent 24. A balloon contains 9.65E24 molecules of H2(e).8.5E24 molecules of Ne(e) and 1.72E25 molecules of He (z). The total pressure in the balloon is 127kPa. What is the partial pressure of each of the gases? Ans: H2=34.7kPa;Ne=30.5kPa;He=61.8kPa 25. A glass bulb contains 10.0g of O2,15.0g of N2 and 20.0g of Ar. If the partial pressure of O2 is 33kPa, what is the total pressure in the bulb? Ans: 142kPa 26. A large 245 litre steel container at 25C is filled with a mixture of two gases, X and Y. The pressure in the container is 1 atm. There are three moles of gas X and 140g of gas Y. Calculate: a) the total number of moles of gas in the container b) the partial pressure of each gas c) the molar mass of gas Y Ans: a) 10 moles b) X=0.3 atm; Y=0.7atm c) 20g/mol