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Unformatted text preview: CHEM111 Week 5 Discussion Questions Fall 2014 1) The density of an unknown gas is 1.72 g/L at 750.0 torr and 30.0oC. Which of the following could be the unknown gas? [R = 0.0821 L atm / mol K ; R = 8.314 J / mol K ; 1 atm = 760 torr] CS2 NO N2O NH3 NO2 2) A 10.0 L flask contains 0.200 moles of methane, 0.300 moles of hydrogen, and 0.400 moles of nitrogen at 25oC. What is the pressure, in atmospheres, inside the flask? What is the partial pressure of each component of the mixture of gases? What is the mole fraction of the three gasses? [R = 0.0821 L atm / mol K ; R = 8.314 J / mol K] 3) If a barometer were built using water (d = 1g/cm3) instead of mercury (d=13.6 g/cm3), would the column of water be higher than, lower than, or the same as the column of mercury at 1.00 atm? If the level is different, by what factor? Explain. 4) A flask that can withstand an internal pressure of 2500 torr, but no more, is filled with a gas at 21.0oC and 758 torr and heated. At what temperature will it burst? 5) A glass vessel contains 28 g nitrogen gas. Assuming ideal behavior, which of the processes listed below would double the pressure exerted on the walls of the vessel? a) Adding enough mercury to fill one-‐half the container. b) Raising the temperature of the container from 30. oC to 60. oC. c) Raising the temperature of the container from -‐73oC to 127oC. d) Adding 28 g nitrogen gas (inert gas). 6) Nitroglycerine, the explosive ingredient in dynamite, decomposes violently when shocked to form three gasses (N2, CO2, O2) as well as water: C3H5(NO3)3(l) → N2(g) + CO2(g) + O2(g) + H2O(l) a) Balance this equation b) Calculate how many moles of each gas are created in the explosion of 1kg of nitroglycerine. c) What volume would these gasses occupy at 1.0 atm? d) What are the partial pressures of each gas under these conditions? 7) In the “Methode Champenoise,” grape juice is femented in a wine bottle to produce sparkling wine. The reaction is: C6H12O6(aq) ! 2C2H5OH(aq) + 2CO2(g). Fermentation of 750. mL grape juice (density = 1.0 g/cm3) is allowed to take place in a bottle with a total volume of 825 mL until 12% by volume is ethanol (C2H5OH). Assuming that the CO2 is insoluble in H2O (actually a wrong assumption), what would be the pressure of CO2 inside the wine bottle at 25oC? (The density of ethanol is 0.79 g/cm3.) 8) A 1.5 L balloon is filled with a mixture of helium and nitrogen. Assuming that this occurs at 25oC and atmospheric pressure (1.00 atm), determine the following: a) How many total moles of gas were used to fill the balloon? b) If the partial pressure of He in the balloon is 0.8atm, what is the partial pressure of N2 in the balloon? What are the mole fractions of He and N2 in the balloon? c) What is the density of He in this balloon? d) Which of these two gasses would you expect to effuse out of the balloon faster and why? 9) A compound contains only C, H, and N. It is 58.51% C and 7.37% H by mass. Helium effuses through a porous frit 3.20 times as fast as the compound does. Determine the empirical and molecular formulas of this compound. ...
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- Spring '08
- Chemistry, 1g, 1Kg, 12%, 1.0 g, 7.37%, 1.5 L