1. A sample of gaseous uranium hexafluoride, UF6, is held at a temperature of 300 K and a pressure of 0.1 mbar. The coll

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1 A Sample Of Gaseous Uranium Hexafluoride Uf6 Is Held At A Temperature Of 300 K And A Pressure Of 0 1 Mbar The Coll 1 (64.7 KiB) Viewed 45 times

1. A sample of gaseous uranium hexafluoride, UF6, is held at a temperature of 300 K and a pressure of 0.1 mbar. The collision diameter of UFs is 0.40 nm. (0) Calculate the root-mean-square (r.m.s.) speed of the molecules. Make sure to show all units in your working and how the units cancel out. [5 marks] (11) Estimate the mean free path and collision frequency under these conditions. [10 marks) 2. Self-contained underwater breathing apparatus (SCUBA) lets divers breathe underwater by supplying their own source of breathing gas, usually compressed air. A 10 dm SCUBA cylinder is filled with air to a pressure of 300 atm at a temperature of 20°C. (0) Calculate the amount in moles of gas in the cylinder, assuming air behaves as an ideal gas. Show how your units cancel out. (6 marks) (11) When the diver jumps into cold water at 278 K, the pressure gauge shows an alarming drop in pressure. Calculate the new pressure inside the cylinder. [3 marks] Compressed gases do not behave as ideal gases. Explain why. [3 marks] (iv) Use the van der Waals equation to show that the amount of compressed air in the cylinder is 115 mol. For air, a = 0.137 m Pa mol-2 and b = 3.7 x 10-5 mmol-Hint: Instead of solving for n, show that the pressure calculated for 115 mol is consistent with 300 atm. Show how your units cancel out. [3 marks] (v) Comparing the amount of air calculated using the ideal gas equation (part (0) and the amount of air calculated in part (iv), comment on the difference and its implication for divers. [3 marks]