1. [Chang7 5.P.013.] Convert 295 mmhg to kpa. kpa Convert 2.0 kpa to mmhg. mmhg

Transcription

1 Score 1. [Chang7 5.P.013.] Convert 295 mmhg to kpa. kpa Convert 2.0 kpa to mmhg. mmhg 2. [Chang7 5.P.019.] The volume of a gas is 5.80 L, measured at 1.00 atm. What is the pressure of the gas in mmhg if the volume is changed to 8.54 L? (The temperature remains constant.) mmhg

2 3. [Chang7 5.P.033.] A gas-filled balloon having a volume of 5.50 L at 1.2 atm and 25 C is allowed to rise to the stratosphere (about 30 km above the surface of Earth), where the temperature and pressure are -23 C and atm, respectively. Calculate the final volume of the balloon. L 4. [Chang7 5.P.059.] Dry air near sea level has the following composition by volume: N 2, percent; O 2, percent; Ar, 0.93 percent; CO 2, 0.05 percent. The atmospheric pressure is 1.00 atm. (Hint: Since volume is proportional to the number of moles present, mole fractions of gases can be expressed as ratios of volumes at the same temperature and pressure.) (a) Calculate the partial pressure of each gas in atm. P N2 P O2 atm P Ar atm atm P CO2 atm (b) Calculate the concentration of each gas in moles per liter at 0 C. C N2 C O2 M C Ar M M

3 C CO2 M 5. [Chang7 5.TB.003a.] Define pressure. force applied per unit volume volume per unit force area per unit force force applied per unit area 6. [Chang7 5.TB.003b.] Give the common units for pressure. mmh 2 O atm, kpa mmhg, atm, kpa, mmh 2 O, atm, Pa mmhg, atm, liters

4 7. [Chang7 5.TB.004b.] Most manometers are used to measure atmospheric pressure. true false 8. [Chang7 5.TB.005.] Why is mercury a more suitable substance to use in a barometer than water? Mercury is less dense than water. Mercury has a higher freezing point than water. Mercury is more dense than water. Mercury doesn't vaporize. 9. [Chang7 5.TB.008.] Is the atmospheric pressure in a mine that is 500 m below sea level greater or less than 1 atm? greater than 1 atm less than 1 atm

5 10. [Chang7 5.TB.009a.] What is the difference between a gas and a vapor? A gas is the gaseous form of any substance; a vapor refers to a gas over a water surface. A gas and a vapor are two interchangeable nomenclatures; they are idenctical. A gas is a substance normally in the gaseous state at normal atmospheric conditions (25C, 1 atm); a vapor is a gas over a water surface. A gas is a susbstance normally in the gaseous state at normal atmospheric conditions (25C, 1 atm); a vapor is the gaseous form of any substance that is a liquid or a solid at normal temperatures and pressures. 11. [Chang7 5.TB.009b.] At 25 C, which of the following substances in the gas phase should be properly called a gas and which should be called a vapor: molecular nitrogen (N 2 ), mercury (Hg)? N 2 is a vapor; Hg is a vapor N 2 is a gas; Hg is a gas N 2 is a vapor; Hg is a gas. N 2 is a gas; Hg is a vapor

6 12. [Chang7 5.TB.012.] Why do astronauts have to wear protective suits when they are on the surface of the moon? (Select all that apply.) The atmosperic pressure on the moon is too low, their cells would all rupture and release gasses, killing them. The atmosperic pressure on the moon is too high, it would crush them. None of these. The temperatures are too cold, or too hot, to sustain life for long; and there is no oxygen to breathe. 13. [Chang7 5.TB.016.] Explain why a helium weather balloon expands as it rises in the air. Assume that the temperature remains constant. The atmosperic pressure outside the balloon increases, and the gas inside expands to equal that pressure. Pressure and volume are directly proportional at constant temperature. The atmosperic pressure outside the balloon decreases, and the gas inside expands to equal that pressure. The number of moles of gas increase as the balloon rises.

7 14. [Chang7 5.TB.026.] Write the ideal gas equation. Give the units for each term in the equation. PV = nrt; P in torr, V in L, n in mol, R in Latm/Kmol, T in K. PV = nrt; P in atm, V in L, n in mol, R in Latm/Kmol, T in K. PV = nrt; P in torr, V in L, n in mol, R in Latm/Kmol, T in C. PV = nrt; P in atm, V in L, n in mol, R in Latm/Kmol, T in C. 15. [Chang7 5.TB.025.] Which is not a characteristic of an ideal gas? The molecules of an ideal gas repel one another. The volume of the ideal gas molecules is negligible compared to the volume of the container. The molecules of an ideal gas do not attract one another. The pressure, volume, temperature relationship of this gas fits the ideal gas equation. 16. [Chang7 5.TB.027b.] What is the volume of one mole of an ideal gas at STP? 10.0 L 1.0 L 24.5 L 22.4 L

8 17. [Chang7 5.TB.028a.] Why is the density of a gas much lower than that of a liquid or solid under atmospheric conditions? (Select all that apply.) Gas molecules are not very compressible. None of these. Gas molecules are separated by distances that are large compared to their size. There are much smaller intermolecular forces between gas molecules. 18. [Chang7 5.TB.047.] A certain anesthetic contains 64.9 percent C, 13.5 percent H, and 21.6 percent O by mass. At 120 C and 750 mmhg, 1.00 L of the gaseous compound weighs 2.30 g. What is the molecular formula of the compound? C 4 H 10 O 2 C 2 H 5 O C 4 H 10 O C 8 H 20 O [Chang7 5.TB.054.] Ethanol (C 2 H 5 OH) burns in air. C 2 H 5 OH(l) + O 2 (g) CO 2 (g) + H 2 O(l) Balance the equation and determine the volume of air in liters at 35.0 C and 790 mmhg required to burn 227 g of ethanol. Assume that air is 21.0 percent O 2 by volume. 1,710 L 360 L 75.6 L

9 571 L 20. [Chang7 5.TB.055a.] Refer to Dalton's law of partial pressures and explain what mole fraction is. The ratio of the number of moles of one component to the number of moles of all components present. The number of moles of one component divided by 100. The ratio of the number of moles of all components present to the number of moles of one component. The number of moles of one component. 21. [Chang7 5.TB.055b.] Does mole fraction have units? yes, mol no yes, mol -1

10 22. [Chang7 5.TB.097.] Nitric oxide (NO) reacts with molecular oxygen as follows. 2 NO(g) + O 2 (g) 2 NO 2 (g) Initially NO and O 2 are separated as shown below. When the valve is opened, the reaction quickly goes to completion. Determine what gases remain at the end and calculate their partial pressures. Assume that the temperature remains constant at 25 C. Partial pressures: O 2 = atm; NO 2 = atm Partial pressures: O 2 = 1.98 atm; NO 2 = 3.97 atm Partial pressures: O 2 = atm; NO 2 = atm Partial pressures: O 2 = atm; NO 2 = atm 23. [Chang7 5.TB.104b.] Commercially, compressed oxygen is sold in metal cylinders. Suppose a 120 L cylinder is filled with oxygen to a pressure of 132 atm at 22 C. How many liters of O 2 gas at 1.00 atm and 22 C could the cylinder produce? Assume ideal behavior L L L L

11 24. [Chang7 5.TB.127.] Lithium hydride reacts with water as follows. LiH(s) + H 2 O(l) LiOH(aq) + H 2 (g) During World War II, U.S. pilots carried LiH tablets. In the event of a crash landing at sea, the LiH would react with the seawater and fill their life belts and lifeboats with hydrogen gas. How many grams of LiH are needed to fill a 4.1 L life belt at 0.97 atm and 12 C? 0.7 g 2.8 g 1.4 g 21 g it all questions for grading Save all work Home My Assignments by North Carolina State University. All rights reserved.