1 Chem1A Unit 2 Answers CHAPTERS 5 6 7 8 Information that will be available 34 8 7 h 6 6262 x 10 J s c 3 00 x 10 m s R 1 097 x 10 m 1 B RH 2 179 x 10 18 J En B n2 c E h h mu me 9 11 x 10 31 kg 1 R 1 nf2 1 ni2 Bonus problems due at start of test SHOW WORK on the test for full credit 1 1 Convert 748 torr to the following units a atm b Pa c bar d psi a 0 984 atm b 9 97 x 104 Pa c 0 997 bar d 14 5 psi 2 Hydrogen gas is produced by the reaction of sodium metal with an excess of hydrochloric acid solution The hydrogen gas was collected by water displacement at 22 C in a 127 ml container with a total pressure of 748 torr The vapor pressure of water at 22 C is 19 8 torr a What mass of sodium metal was consumed in the reaction 0 231 g Na b What is the volume of dry H2 gas at STP 0 113 L 3 A foul smelling gas produced by the reaction of H2SO2 with Na2S was collected A 2 00 L sample had a mass of 3 04 grams at STP Solve for the molecular weight of the gas and determine its likely identity MW 34 0 g mol H2S g 4 Two separate containers have the same volume and temperature The first contains 0 50 moles of CO2 gas and the second contains 0 75 moles of CH4 gas State if the following properties of CO2 are greater than less than or equal to these properties of CH4 a Pressure of gas in containers CO2 is CH4 b Density of gas in containers CO2 is CH4 5 A 4 50 liter helium balloon is given to a small child by the sea It is a nice warm day of 30 C and 1 atm pressure Unhappily the child lets go of the balloon and it rises up into the air At a new higher altitude the pressure is 703 torr and Temperature is 10 C What is the new volume of the balloon 4 54 L 6 The density of a gas at STP is 0 7143 g L Is this gas CH4 Ar CO2 or Cl2 MW 16 0 g mol CH4 2 7 The velocity of H2 gas is found to be 4 36 times the velocity of an unknown gas Calculate the molecular weight of the unknown gas Given that this gas is one of the diatomic elements what is the unknown gas 38 0 g mol F2 8 a b c What are the characteristics kinetic molecular theory of an ideal gas See notes How is a real gas different and under what circumstances does a gas become less ideal Real gasses have attractions and take up some space What is the Van der Waals equation P d V nb nRT How are the constants a and b affected by size of molecule and intermolecular attractions a is larger as attractions are stronger b increases with the bigness or size 9 Consider a sample of 1 000 mole CO2 gas confined to a volume of 3 000 liters at 0 0 C Calculate the pressure of the gas using a the ideal gas equation and b the van der Waals equation For CO2 a 3 59 L2atm mol2 and b 0 0427 L mol a P 7 47 atm b P 7 18 atm 10 How did the relationship between volume and temperature of a gas at constant pressure and number of moles help determine absolute zero temperature When the volume is extrapolated to zero the Temperature 273 C or 0K 11 What is the volume of 32 7 grams of F2 gas at STP 19 3 L 12 What is the number of moles of gas in a 550 ml container at 30 0 C and 751 torr pressure 0 0219 mol 13 534 mL of CH4 gas was collected at 23 C and 754 torr What new volume would the CH4 gas occupy at 732 torr and 46 C 593 ml 14 Carbon dioxide gas CO2 is collected over water in a 544 ml container at 23 0 C and equalized with the room pressure of 750 torr The vapor pressure of water at 23 0 C is 21 1 torr What volume will this same sample of dry CO2 gas occupy under STP conditions 486 ml 3 15 127 ml of N2 gas was collected by displacement of water at 25 C and 742 torr What is the number of moles of N2 gas The vapor pressure of water at 25 C is 24 torr 0 00491 mol 16 Solve for the mole fraction of each component in a mixture of 12 0 g H2 60 0 g N2 and 2 50 g of NH3 gases Solve for the total pressure and partial pressures of each if the gas mixture is in a 100 0 L container at 22 5 C 6 0 mole H2 2 14 mol N2 0 147 mol NH3 XH2 0 724 XN2 0 258 XNH3 0 018 Ptotal 2 01 atm PH2 1 455 atm PN2 0 518 atm PNH3 0 036 atm 17 a b 18 Balance the following unbalanced equation C5H12 g O2 g CO2 g H2O g C5H12 g 8 O2 g 5 CO2 g 6 H2O g What volume of CO2 gas at STP will be produced from 144 g of C5H12 224 L A 2 135 g gas sample occupies 315 5 ml at 739 2 mm Hg and 26 1 C Analysis of the compound shows it to be 14 05 C 41 48 Cl and 44 46 F by mass What is the molecular formula Empirical formula CClF2 MW 171 g mol Molecular Formula C2Cl2F4 19 Typically when a person coughs he or she first inhales about 2 0 L of air at 1 0 atm pressure and 25 C The epiglottis and the vocal cords then shut trapping the air in the lungs where it is warmed to 37 C and compressed to 1 7 L by action of the diaphragm and chest muscles The sudden opening of the epiglottis and vocal cords releases this air explosively What is the approximate pressure of the gas inside the lungs just before the cough 1 22 atm 20 a Which has the smaller root mean squared speed rms at 27 C O2 or HF O2 is heavier and slower b Calculate the rms at 27 C for the one with slower speed 484 m s 21 A sample of Ar g effuses through a tiny hole in 45 1 seconds How long would it take for a sample of SF4 gas to effuse under the same conditions 74 2 s 4 22 Balance the equation and calculate the liters of CO2 gas produced for every 9 00 m3 of O2 gas consumed in the combustion reaction below Both CO2 and O2 gases are …