1Exam 4 Practice Problems ____ 1. Which of the following statements is false? a. Condensed states have much higher densities than gases. b. Molecules are very far apart in gases and closer together in liquids and solids. c. Gases completely fill any container they occupy and are easily compressed. d. Vapor refers to a gas formed by evaporation of a liquid or sublimation of a solid. e. Solid water (ice), unlike most substances, is denser than its liquid form (water). ____ 2. Which statement is false? a. The density of a gas is constant as long as its temperature remains constant. b. Gas expands without limit. c. Gases diffuse into each other and mix almost immediately when put into the same container. d. The molecular mass of a gaseous compound is an invariable quantity. e. Pressure must be exerted on a sample of a gas in order to confine it. ____ 3. If the volume of a sample of Ne is tripled while the temperature is held constant, what happens to the pressure of the gas? a. It triples b. It stays the same. c. It doubles. d. It decreases by 1/3. e. It decreases by 1/2. ____ 4. A sample of a gas occupies 1600. milliliters at 20.0°C and 600. torr. What volume will it occupy at the same temperature and 800. torr? a. 1.00 × 103 mL b. 1.20 × 103 mL c. 1.45 × 103 mL d. 2.02 × 103 mL e. 2.13 × 103 mL ____ 5. Ammonia, NH3, is used to as fertilizer and as a refrigerant. What is the new pressure if 25.0 g of ammonia with a volume of 750 mL at 1.50 atm is expanded to 7.50 L at constant temperature? a. 15 atm b. 114 mm Hg c. 0.15 psi d. 6.67 atm e. 15 mm Hg ____ 6. A sample of oxygen occupies 47.2 liters under a pressure of 1240. torr at 25°C. By what percent does the volume of this sample change if the pressure were decreased to 730. torr at 25°C? a. 37.8% b. 41.1% c. 43.4% d. 46.1% e. 69.9% ____ 7. If the volume of a sample of Cl2 gas is tripled while pressure is held constant, what happens to the absolute temperature? a. It remains constant. b. It decreases by 1/3. c. It triples. d. It increases nine-fold. e. It decreases by 1/6.2____ 8. Radon is a radioactive gas found below ground. If a sample of radon occupies 29 mL at 25 °C, what volume will it occupy at 500 K? Assume constant pressure. a. 5140 mL b. 29 mL c. 49 mL d. 17 mL e. 500 mL ____ 9. A sample of nitrogen occupies 5.50 liters under a pressure of 900. torr at 25.0°C. At what temperature will it occupy 10.0 liters at the same pressure? a. 32°C b. -109°C c. 154°C d. 269°C e. 370°C ____ 10. A sample of helium occupies 5.00 L at STP. What volume will the sample occupy at 0.0°C and 890. torr? a. 3.56 L b. 3.72 L c. 4.06 L d. 4.27 L e. 5.86 L ____ 11. Which of the following statements about the combined gas law is incorrect? a. At constant temperature the volume occupied by a definite mass of a gas varies inversely with the applied pressure. b. Doubling the volume and pressure of a sample of gas quadruples the absolute temperature.c. At constant pressure the volume occupied by a definite mass of a gas varies inversely with the absolute temperature. d. Halving the volume of a sample of gas while doubling the pressure leaves the absolute temperature unchanged. e. Doubling the volume and pressure of a sample of gas doubles the absolute temperature. ____ 12. A 1 L sample of gas at 25°C and 1 atm pressure is subjected to an increase in pressure and a decrease in temperature. The density of the gas __________. a. decreases b. increases c. remains the same d. becomes zero e. either increases or decreases, depending on the sizes of the pressure and temperature changes ____ 13. What is the volume occupied by 10.0 grams of NH3 at STP, if it behaves ideally? a. 10.6 L b. 13.2 L c. 14.3 L d. 14.9 L e. 15.8 L ____ 14. What is the molecular weight of a gas if 0.104 gram of the gas occupies 48.7 mL at STP? a. 5.06 g/mol b. 28.2 g/mol c. 34.5 g/mol d. 40.0 g/mol e. 47.8 g/mol3____ 15. Given the mass of one mole of gaseous NO is 30.0 grams/mole, calculate the density of NO in grams/liter at STP. a. 1.12 g/L b. 0.987 g/L c. 2.17 g/L d. 1.34 g/L e. 1.60 g/L ____ 16. Calculate the density of O2, in g/L, at STP. a. 0.810 g/L b. 1.43 g/L c. 1.62 g/L d. 0.714 g/L e. 1.14 g/L ____ 17. What is the volume that 57.0 grams of F2 would occupy at 227°C and 1.50 atm? a. 1.06 L b. 18.6 L c. 41.0 L d. 82.1 L e. 106 L ____ 18. How many oxygen atoms are contained in a sample of O2 that occupies 1500. mL at 50.0°C and 1.00 atm pressure? a. 1.75 × 1023 b. 3.87 × 1023 c. 3.40 × 1022 d. 8.91 × 1022 e. 6.81 × 1022 ____ 19. 0.397-g sample of a gas occupies a volume of 275 mL at 10.°C and 365 torr. What is the molecular weight of the gas? a. 85.9 g/mol b. 72.8 g/mol c. 69.8 g/mol d. 61.3 g/mol e. 59.8 g/mol ____ 20. What is the pressure exerted by a mixture of 14.0 grams of N2, 71.0 grams of Cl2, and 16.0 grams of He in a 50.0-liter container at 0°C? a. 2.47 atm b. 6.80 atm c. 14.1 atm d. 4.66 atm e. 0.687 atm ____ 21. A mixture of gas contains 0.251 g Ar and 1.95 g Xe and has a total pressure of 2.33 atm. What are the partial pressures of each gas? PAr (atm) PXe (atm) a. 1.61 0.72 b. 0.72 1.61 c. 1.17 1.16 d. 0.27 2.06 e. 0.30 2.03 ____ 22. A 10.0-liter vessel contains gas A at a pressure of 300. torr. A 3.0-liter vessel contains gas B at a pressure of 400. torr. Gas A is forced into the second vessel. Calculate the resulting pressure in torr. Assume temperature remains constant.4a. 1000 torr b. 1400 torr c. 1800 torr d. 2000 torr e. 2300 torr ____ 23. A 75 mL sample of CO2 is collected over water at 25 °C when the atmospheric pressure is 1.05 atm. How many moles of CO2 are present? The vapor pressure of water at 25 °C is 24.3 torr. a. 3.12 b. 0.0372 c. 0.00312 d. 2.37 e. 0.0322 ____ 24. Consider the following gas phase reaction. 4HCl(g) + O2(g) → 2Cl2(g) + 2H2O(g) What volume of chlorine at STP can be prepared from the reaction of 600. mL of gaseous HCl, measured at STP, with excess O2, assuming that all the HCl reacts? a. 150. mL b. 267 mL c. 300. mL d. 425 mL e. 600. mL ____ 25. Calculate the weight of KClO3 that would be …