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AP Chem Mr. Dehne
Name: __________________________________
Date: __________________
Per#: ___
AP Chem
Gases Topic #5 Worksheet Packet
(You must SHOW WORK for any question involving calculations)
Gases WS#1 (Pressure/Gas Laws (5pts))
1. Feon-12 (CF2Cl2) is commonly used as the refrigerant in central home air conditioners. The system is initially charged to a
pressure of 4.8atm. Express the pressure in each of the following units (1atm = 14.7psi).
a. mmHg
b. torr
c. Pa
d. psi
2. An aerosol can contains 400.mL of compressed gas at 5.20atm pressure. When all the gas is sprayed into a large plastic bag,
the bag inflates to a volume of 2.24L, What is the pressure of gas inside the plastic bag? Assume temperature is constant.
3. If 0.500mol of nitrogen gas occupies a volume of 11.2L at 0oC, what volume will 2.00mol of nitrogen gas occupy at the same
temperature?
4. Complete the following table for an ideal gas.
P(atm)
V(L)
n(mol)
T
3
a.
7.74x10 Pa
12.2L
25oC
b.
43.0mL
0.421
223K
-2
c.
455torr
4.4x10 mol
331oC
d.
745mmHg
11.2L
0.41mol
5. Suppose two 200.0L tanks are to be filled separately with the gases helium and hydrogen. What mass of each gas is needed to
produce a pressure of 135atm in its respective tank at 24 oC?
6. A 2.50L container is filled with 175g argon.
a. If the pressure is 10.0atm, what is the temperature?
b. If the temperature is 225k, what is the pressure?
7. A particular balloon is designed by its manufacturer to b e inflated to a volume of no more than 2.5L. If the balloon is filled
with 2.0L of helium at sea level, is released, and rises to an altitude at which the atmospheric pressure is only500.mmHg, will
the balloon burst? (Assume temperature is constant.)
8. A compressed gas cylinder, at 13.7Mpa and 23 oC, is in a room where a fire raises the temperature to 450oC. What is the new
pressure in the cylinder?
9. An ideal gas is contained in a cylinder with a volume of 5.0x10 2mL at a temperature of 30oC and a pressure of 710.torr. The
gas is then compressed to a volume of 25mL, and the temperature is raised to 820. oC. What is the new pressure of the gas?
10. A hot air balloon is filled with air to a volume of 4.00x10 3m3 at 745torr and 21oC. The air in the balloon is then heated to
62oC, causing the balloon to expand to a volume of 4.20x10 3m3. What is the ratio of the number of moles of air in the heated
balloon to the original number of moles of air in the balloon? (Hint: Openings in the balloon allow air to flow in and out.
Thus the pressure in the balloon is always the same as that of the atmosphere.)
Gases WS#2 (Gas Density/Molar Mass, and Reaction Stoichiometry (5pts))
1. What mass of helium is required to fill a 1.4L balloon at STP?
2. Consider the following unbalanced chemical equation: C6H12O6(s) + O2(g)→CO2(g) + H2O(g). What volume of oxygen gas,
measured at 28oC and 0.976atm, is needed to react with 5.00g of C6H12O6? What volume of each product is produced under
the same conditions?
3. In 1897 the Swedish explorer Andree tried to reach the North Pole in a balloon. The balloon was filled with hydrogen gas.
The hydrogen gas was prepared from iron splints and diluted sulfuric acid. The reaction is Fe(s) + H2SO4(aq) → FeSO4(aq) +
H2(g). The volume of the balloon was 4800m3 and the loss of hydrogen gas during filling was estimated at 20.%.What mass
of iron splints and 98% (by mass) H2SO4 were needed to ensure the complete filling of the balloon? Assume a temperature of
0oC, a pressure of 1.0atm during filling, and 100% yield.
4. Consider the reaction between 50.0mL of liquid methyl alcohol, CH3OH (density = 0.850g/mL), and 22.8L of O 2 at 27oC and
a pressure of 2.00atm. The products of the reaction are CO 2(g) and H2O(g). Calculate the number of moles of H2O formed if
the reaction goes to completion.
1
5.
Hydrogen cyanide is prepared commercially by the reaction of methane, CH 4(g), ammonia, NH3(g), and oxygen, O2(g), at
high temperature. The other product is gaseous water.
a. Write a chemical equation for the reaction.
b. What volume of HCN(g) can be obtained from 20.0L CH 4(g), 20.0L NH3(g), and 20.0L O2(g)? The volumes of all
gases are measured at the same temperature and pressure.
6. A gas consisting of only carbon and hydrogen (hydrocarbon) has an empirical formula of CH2. The gas has a density of
1.65g/L at 27oC and 734torr. Determine the molar mass and molecular formula of the gas.
7. Silicon tetrachloiride (SiCl4) and trichlorosilane (SiHCl3) are both starting materials for the production of electronics-grade
silicon. Calculate the densities of pure SiCl4 and pure SiHCl3 vapor at 85oC and 758torr.
Gases WS#3 (Partial Pressure/Kinetic Molecular Theory and Real Gases (5 pts))
1. A piece of solid carbon dioxide, with a mass of 7.8g, is placed in a 4.0L otherwise empty container at 27oC. What is the
pressure in the container after all the carbon dioxide vaporized? If 7.8g solid carbon dioxide were placed in the same
container bit it already contained air at 740torr, what would be the partial pressure of carbon dioxide and the total pressure in
the container after the carbon dioxide vaporizes?
2. Consider the flask in the following diagram. What are the final partial pressures of H 2 and N2 after the stopcock between the
two flasks is opened? (Assume the final volume is 3.00L.) What is the total pressure (in torr)?
2.00L H2
475torr
1.00L N2
0.200 atm
3.
The partial pressure of CH4(g) is 0.175atm and that of O2(g) is 0.250atm in a mixture of two gases.
a. What is the mole fraction of each gas in the mixture?
b. If the mixture occupies a volume of 10.5L at 65oC, calculate the total number of moles of gas in the mixture.
c. Calculate the number of grams of each gas in the mixture.
4. Small quantities of hydrogen gas can be prepared in the laboratory by the addition of aqueous hydrochloric acid to metallic
zinc. Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g). Typically, the hydrogen gas is bubbled through water for collection and
becomes saturated with water vapor. Suppose 240.mL of hydrogen gas is collected at 30. oC and has a total pressure of
1.032atm by this process. What is the partial pressure of hydrogen gas in the sample? How many grams of zinc must have
reacted to produce this quantity of hydrogen? (The vapor pressure of water is 32torr at 30 oC.)
5. At elevated temperatures, sodium chlorate decomposes to produce sodium chloride and oxygen gas. A 0.8765g sample of
impure sodium chlorate was heated until the production of oxygen ceased. The oxygen gas collected over water occupied
57.3mL at a temperature of 22 oC and a pressure of 734torr. Calculate the mass percent of NaClO 3 in the original sample. (At
22oC the vapor pressure of water is 19.8torr.)
6. Calculate the average kinetic energy of the CH4 molecules in a sample of CH4 gas at 273K and 546K.
7. Calculate the root mean square velocity of the CH4 molecules in a sample of CH4 gas at 273K and at 546K.
8. Consider a 1mol sample of CH4(g) at 273K. If the temperature is increased, what happens to the average kinetic energy and
average velocity of the CH4 molecules? Explain.
9. Consider three identical flasks filled with different gases.
Flask A: CO at 760torr and 0oC
Flask B: N2 at 250torr and 0oC
Flask C: H2 at 100torr and 0oC
a. In which flask will the molecules have the greatest average kinetic energy?
b. In which flask will the molecules have the greatest average velocity?
10. The effusion rate of an unknown gas is measured and found to be 31.50mL/min. Under identical experimental conditions, the
effusion rate of O2 is found 30.50mL/min. If the choices are CH 4, CO, NO, CO2, and NO2, what is the identity of the
unknown gas?
11. One method of separating oxygen isotopes is by gaseous diffusion of carbon monoxide. The gaseous diffusion process
behaves like an effusion process. Calculate the relative rates of effusion of 12C16O, 12C17O, and 12C18O. Name some
advantages and disadvantages of separating oxygen isotopes by gaseous diffusion of carbon dioxide instead of carbon
monoxide.
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Gases WS#4 (Conceptual Problems)
1. Draw a quantitative graph to show how the first property varies with the second in each of the following (assume 1mol of an
ideal gas and T in Kelvin).
a. PV versus V with constant T
b. P versus T with constant V
c. T versus V with constant P
d. P versus V with constant T
e. P versus 1/V with constant T
f. PV/T versus P
2. A 2.747g sample of manganese metal is reacted with excess HCl gas to produce 3.22L of H 2(g) at 373K and 0.951atm and a
manganese chloride compound (MnClx). What is the formula of the manganese chloride compound produced in the reaction?
3. A 15.0L tank is filled with H2 to a pressure 2.00x102atm. How many balloons (each 2.00L) can be inflated to a pressure of
1.00atm from the tank? Assume that there is no temperature change and that the tank cannot be emptied below 1.00atm
pressure.
4. A 2.00L sample of O2(g) was collected over water at a total pressure of 785torr and 25 oC . When the O2(g) was dried (water
vapor removed), the gas had a volume of 1.94L at 25oC and 785torr. Calculate the vapor pressure of water at 25 oC.
5. Metallic molybdenum can be produced from the mineral molybdenite, MoS2. The mineral is first oxidized in air to
molybdenum trioxide and sulfur dioxide. Molybdenum triocide is then reduced to metallic molybdenum using hydrogen gas.
The balanced equations are
MoS2(s) + 7/2O2(g) → MoO3(s) + 2SO2(g)
MoO3(s) + 3H2(g) → Mo(s) + 3H2O(l)
Calculate the volumes of air and hydrogen gas at 17 oC and 1.00atm that are necessary to produce 1.00x103kg of pure
molybdenum from MoS2. Assume air contains 21% oxygen by volume and assume 100% yield for each reaction.
6. In the “Method Champenoise,” grape juice is fermented in a wine bottled to produce sparkling wine. The reactions is
C6H12O6(aq) → 2C2H5OH(aq) + 2CO2(g). Fermentation of 750.mL grape juice (density = 1.0g.cm3) is allowed to take place
in a bottle with at total volume of 825mL until 12% by volume is ethanol (C 2H5OH). 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 0.79g/cm3.)
7. One of the chemical controversies of the nineteenth century concerned the element beryllium (Be). Berzelius originally
claimed that beryllium was a trivalent element (forming Be3+ ions) and that it gave an oxide with the formula Be2O3. This
resulted in a calculated atomic mass of 13.6 for beryllium. In formulating his periodic table, Mendeleev proposed that
beryllium was divalent (forming Be2+ ions) and that it gave an oxide with the formula BeO. This assumption gives an atomic
mass of 9.0. In 1894, A. Combes (Comptes Rendus 1894, p.1221) reacted beryllium with the anion C5H7O2- and measured the
density of the gaseous product. Combes’s data for two different experiments are as follows:
I
II
Mass
0.2022g
0.2224g
Volume
22.6cm3
26.0cm3
Temperature
13oC
17oC
pressure
765.2mmHg
764.6mm
If beryllium is a divalent (2+) metal, the molecular formula of the products will be Be(C5H7O2)2; if it is trivalent, (3+), the
formula will be Be(C5H7O2)3. Show how Combes’s data help to confirm that beryllium is a divalent metal.
8. The nitrogen content of organic compounds can be determined by the Dumas method. The compound in question is first
reacted by passage over hot CuO(s): compound Hot
→ N2(g) + CO2(g) + H2O(g). The product gas is then passed through
CuO(s)
concentrated solution of KOH to remove the CO2. After passage through the KOH solution, the gas contains N 2 and is
saturated with water vapor. In a given experiment a 0.253g sample of a compound produced 31.8mL N2 saturated with water
vapor at 25oC and 726torr. What is the mass percent of nitrogen in the compound? (The vapor pressure of water at 25 oC is
23.8 torr.)
Extra Credit Problems (+2pts/question,). Answers must be correct with work legible and coherent. No teacher help.
UNDER CONSTRUCTION!
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Answer Key
WS#1
1. (a) 3.6x103mm (b) 3.6x103torr
(c) 4.9x105Pa
(d) 71psi
2. 0.972atm
3. 44.8L
4. (a) 0.0381mol
(b) 179atm
(c) 3.64L
(d) 326K
3
3
5. 4.44x10 g He; 2.24x10 g H2
6. (a) 69.6K
(b) 32.3atm
7. burst
8. 33.5MPa
9. 5.1x104torr
10. Increases from 1.00L to 2.82L, so change in volume is 1.82L.
WS#2
1. 0.27g
2. 4.23L O2; 4.23L CO2; 4.23L H2O
3. 1.5x107g Fe, 2.6x107g 98% H2SO4
4. 2.47mol H2O
5. (a) 2CH4(g) + 2NH3(g) + 3O2(g) 2HCN(g) + 6H2O(g)
(b) 13.3L
6. 42.1g/mol C3H6
7. 5.77g/L (SiCl4), 4.60 g/L (SiHCl3)
WS#3
1. 1.1atm, PCO2 = 1.1atm, PTotal = 2.1atm
2. PH2 = 317torr, PN2 = 50.7torr, PTotal = 368torr
3. (a) XCH4 = 0.412, XO2 = 0.588
(b) 0.161mol
(c) 1.06gCH4, 3.03g O2
4. 0.990atm; 0.625g
5. 18.0%
6. 3.40x103J/mol (273K); 6.81x103J/mol (546K)
7. CH4: 652m/s(273K); 921m/s (546K); N2: 493m/s (273K); 697m/s (546K)
8. Both increase with increased temperature
9. (a) all the same (b) flask C
10. NO
11. 1.04, 1.02, and 1.00. Advantage : CO2 isn’t as toxic as CO. Disadvantages: can get a mixture of isotopes in CO 2, some
species would effuse at the same rate
WS#4
1. Do in class (ask me)
2. MnCl4
3. 1490 balloons
4. 24torr
5. 4.1x106L air; 7.42x105L H2
6. 490atm
7. Be(C5H7O2)2 has a MM of 207g/mol and the MM of Be(C5H7O2)2 is 311g/mol. The MM calculated from the first data set is
209g/mol and from the second data set is 202g/mol. These experiment results are close to the expected value of 207g/mol
Be(C5H7O2)2. Thus we conclude from these data that beryllium is a divalent element with an atomic mass of 9.0amu
8. 13.3% N
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