Chemistry Past Papers Chapter 5

CHAPTER 5 1. 550.0 mL sample of NO gas was collected over water at 25.0oC and an atmospheric pressure of 748 torr. Calculate the mass of dry NO in this sample. Vapor pressure of H2O at 25.0oC = 24 torr, and molar mass of NO = 30.0 g/mol A) 0.374 g B) 0.643 g C) 0.771 g D) 0.421 g E) 0.549 g 2. Which of the following gases has the greatest density at 2.5 atm and 25oC? (Molar masses for C=12.0, H=1.01, N=14.0, O=16.0, S=32.1, and F=19.0 g/mol) A) N2O B) SO2 C) C4H8 D) O2 E) NF3 P a g e 29 | 45 3. Calculate the density of CO2 gas (in g/L) at 25oC and 1.60 atm (molar mass of CO2 = 44.0 g/mol). A) 2.52 B) 2.70 C) 2.88 D) 2.10 E) 2.34 4. A sample of 1.40 g of a vapor occupies 0.559 L at 97oC and 0.967 atm. Calculate the molar mass of the compound. A) 98.3 B) 78.7 C) 124 D) 144 E) 112 5. A mixture of 0.260 moles O2 and 0.540 moles N2 has a total pressure of 4.00 atm. Calculate the partial pressure of O2 in the mixture. A) 1.30 atm B) 2.60 atm C) 3.25 atm D) 0.980 atm E) 1.95 atm P a g e 30 | 45 6. For the following gasses (given molar masses): F2(38), Cl2(71), O2(32), CO2(44) The order of increasing rate of effusion is: A) F2 < Cl2 < CO2 < O2 B) Cl2 < F2 < CO2 < O2 C) Cl2 < O2 < F2 < CO2 D) CO2 < O2 < F2 < Cl2 E) Cl2 < CO2 < F2 < O2 7. The volume of a certain amount of a gas in 8.80 L at 127oC and at pressure of 2.00 atm. Calculate its volume at 27oC and 6.00 atm. A) 6.60 L B) 4.40 L C) 3.30 L D) 2.64 L E) 2.20 L 8. If ideal gas behaviour is assumed, what is the density of Argon (M.W = 39.95) at STP (0oC & 1 atm) in g/L? A) 1.781 B) 448 C) 1.11 D) 0.009 E) 0.901 P a g e 31 | 45 9. A 0.10-gram sample of a diatomic gas occupies a volume of 0.202 L at 0.789 atm and a temperature of 546 K. What is the molar mass in g/mol of the gas sample? A) 32 B) 45 C) 28 D) 38 E) 44 10. Determine the molar mass of a gas if 0.401 L weighs 1.55 g at STP? A) 69.3 g/mol B) 94.5 g/mol C) 86.7 g/mol D) 53.3 g/mol E) 43.3 g/mol 11. In the following chemical reaction, if 20.0 mL of NO2 gas is completely converted to N2O4 gas under the same conditions, what volume (in mL) will N2O4 occupy? Assume an ideal gas behaviour. 2NO2 (g) → N2O4 (g) A) 20.0 B) 10.0 C) 40.0 D) 15.0 P a g e 32 | 45 12. Calculate the density (in g/L) of SO2 gas (molar mass = 64.1 g/mol) at STP conditions. A) 4.11 B) 3.31 C) 2.05 D) 1.52 E) 2.86 13. According to kinetic molecular theory, which of the following statements is correct? A) at same temperature, gases with larger molar masses have lower average kinetic energies. B) the volume by an ideal gas particles can’t be neglected. C) the pressure of the gas is due to the collisions of the gas particles with the walls of the container. D) ideal gas particles repel each other, but don’t attract each other. 14. If 0.10 mole of I2 (M.W = 253.8) vapor can effuse from an opening in a heated vessel in 39 seconds. How long will it take 0.10 mole of H2 (M.W = 2.016) to effuse under the same conditions? A) 9.5 s B) 3.5 s C) 1.8 s D) 5.3 s E) 15.3 s P a g e 33 | 45 15. Calculate the root mean square velocity (urms) in (m/s) of CO2 molecules in a sample of CO2 gas at 1.0oC. (molar mass of CO2 = 44.0 g/mol) A) 394.2 B) 44.0 C) 1.24 D) 39.2 E) 12.5 16. Calculate the mass of Calcium (in g) that must be dissolved in sulfuric acid in order to obtain 500 mL of hydrogen gas at 20oC and 770 mmHg (molar mass of Ca = 40.08 g/mol). Ca (S) + H2SO4 (aq) → CaSO4 (S) + H2 (g) A) 1.38 g B) 0.0425 g C) 1.24 g D) 0.84 g E) 1.13 g 17. The standard temperature and pressure (STP) refers to: A) 237 K & 1 pascal B) 298 K & 1 atm C) 298 K & 1 mmHg D) 273 K & 1 atm E) 0oC & 1 atm P a g e 34 | 45 18. A mixture of 0.100 g H2 (molar mass = 2.02 g/mol) and 0.200 g He (molar mass = 4.00 g/mol) is placed in a 10.0 L container at 2oC. Calculate the total pressure inside the container in atm. A) 0.113 B) 0.225 C) 0.150 D) 0.257 E) 0.450 19. Which of the following is a wrong statement? A) H2 gas behaves more ideally than CO2 gas B) CO2 (44 g/mol) effuses faster than N2 gas (28 g/mol) at STP C) average kinetic energy depends only on temperature D) none of the above is wrong 20. A sample of CO gas has pressure of 58 mmHg and volume of 155 mL. When the CO is transferred to a 1.00 L flask at the same temperature the pressure of the gas in (mmHg) will be? A) 4.34 B) 8990 C) 8.99 D) 111 P a g e 35 | 45