Download ap unit 5 worksheet answers

Name_______________________________________period___________AP Chemistry
Unit 5 answers
Chapters 10, 11.3-11.6
1. Consider two people of the same mass standing in a room. One person is standing normally, and the other is
standing on one foot.
a. Does one person exert greater force on the floor than the other? No
b. Does one person exert a greater pressure on the floor than the other? Yes, the person standing on one foot
exerts more pressure because they are standing on a smaller area
2. Convert the following
a. 265 torr to pascals
b. 675 mmHg to atm
c. 5 atm to kPa
4
3.53 x 10 Pa
0.888 atm
500 kPa
3. A fixed quantity of gas at 23⁰C exhibits a pressure of 748 torr and occupies a volume of 10.3 L. Calculate the
volume the gas will occupy if the temperature is increased to 145 ⁰C
15 L
4. A fixed quantity of gas at 21⁰C exhibits a pressure of 748 torr and occupies a volume of 10.3 L. Calculate the
volume the gas will occupy if the temperature is increased to 36 ⁰C and the pressure is decreased to 700 torr.
12 L
5. Nitrogen and hydrogen gases react to form ammonia gas
a. Write a balanced chemical equation N2 + 3H2  2NH3
b. At a certain temperature and pressure 0.70 L of nitrogen gas reacts with 2.1 L of hydrogen gas. If all the
nitrogen and hydrogen are consumed, what volume of ammonia, at the same temp. and pressure, will
be produced? 1.4 L
6. Calculate the following for an ideal gas
a. The volume of gas if 1.57 mol has a pressure of 0.86 atm at a temperature of -12 ⁰C. 39 L
b. The temp. of a gas of which 0.0679 mol occupies 164 mL at 693 torr. 26.8 K
c. The pressure, in atm, if 0.0825 mol occupies 255 mL at 115⁰C 10.3 atm
d. The grams of nitrogen gas, if 5.49L at 35 ⁰C has a pressure of 11.25 kPa. 0.67 g
7. 23.5 g of CO2 gas is at a temperature of 45oC and a pressure of 125 kPa. What is the volume of the container?
11 L
8. If 128g of a certain gas in a container with a volume of 21.5 L has a pressure of 132 kPa and a temperature of
45oC, what is the molar mass of the gas? 120 g/mol
9. If 4.0 L of a gas were produced at STP and the mass of the gas was found to be 12.8g, then what is the molar
mass of the gas?
72 g/mol
10. a. How many grams of hydrogen gas can be produced by reacting 32.8 g of magnesium according to the
following balanced equation?
Mg (s) + 2 HCl (aq)  MgCl2 (aq) + H2 (g) 2.70 g
b. What volume of hydrogen gas was produced if this reaction was carried out at STP? 30.2 L
11. Nitrogen gas can be produced by reacting Na3N with chlorine gas. If the reaction was carried out at STP with
34.8 g of Na3N, what volume of nitrogen gas can be produced?
4.70 L
12. In a certain combustion reaction involving propane, 34.4 L of CO2 was produced. How many liters of propane
(C3H8) were combusted? Assume the reaction took place at STP.
11.5 L
13. a. Examine the two containers below. Both contain gases that were collected over water. Which one was
collected at the higher temperature—gas A or gas B? Explain your answer. there is more water vapor
Gas A =
Gas B =
Water vapor =
Water vapor =
14. A container of gas with a pressure of 450 kPa contained three different gases—hydrogen, oxygen and nitrogen.
If the partial pressure of hydrogen was 210 kPa and the partial pressure of oxygen was 125 kPa, what was the
partial pressure of nitrogen?
115 kPa
15. A tank held neon gas at a pressure of 3.1 atm, helium at a pressure of 2.7 atm and argon at a pressure of 4.1 atm
What was the pressure in the tank?
9.9 atm
16. Oxygen gas was collected over water at 30oC. The pressure in the 2.5 L container was 110 kPa. If the container
was allowed to expand to 7.0 L and if the temperature was decreased to -30oC, what is the final pressure of the
dry oxygen gas?
30 kPa or 230 torr
17. A quantity of oxygen gas was collected over water at 30oC in a 475 mL container. The pressure in the container
was measured to be 750 torr. How many grams of oxygen gas were collected?
0.6 g
18. How many grams of sodium are required to produce 31.9 L of H2 at 755 mmHg and 290 K according to the
following balanced equation? 2 HNO3 + 2 Na  2 NaNO3 + H2
19.
20.
21.
22.
23.
24.
25.
61 g
Which gas is most dense at 1.00 atm and 298 K? Explain.
a. CO2
b. N2O
c. Cl2
Calculate the density of NO2 gas at 0.970 atm and 35 ⁰C.
1.77 g/L
Calculate the molar mass of a gas if 2.50 g occupies 0.875 L at 685 torr and 35 ⁰C
80.1 g/mol
Calculate the molar mass of a vapor that has a density of 7.135 g/L at 12 ⁰C and 825 torr. 154 g/mol
2Mg (s) + O2(g)  2MgO (s)
If 0.382 L of oxygen is reacted and has a partial pressure of 3.5 x 10-6 torr at 27 ⁰C, what mass of
magnesium will react?
3.5 x 10 -9 g
Ammonium sulfate, an important fertilizer, can be prepared by the reaction of ammonia with sulfuric acid.
a. Write a balanced reaction 2NH3 + H2SO4  (NH4)2SO4
b. Calculate the volume of ammonia needed at 20 ⁰C and 25.0 atm to react with 150 kg of sulfuric acid.
2,940 L
Hydrogen gas is produced when zinc reacts with sulfuric acid
a. Write a balanced chemical reaction. Zn + H2SO4  ZnSO4 + H2
b. If 159 mL of wet hydrogen gas is collected over water at 24 ⁰C and a barometric pressure of 738 torr,
how many grams of zinc has been consumed? 0.402 g
26. A mixture containing 0.538 mol of He gas, 0.315 mol Ne gas, and 0.103 mol Ar gas is confined in a 7.00 L vessel
at 25 ⁰C.
a. Calculate the partial pressure of each gas in the mixture. 1.88 atm He; 1.10 atm Ne; 0.360 atm Ar
b. Calculate the total pressure of the mixture.
3.34 atm
27. A mixture of gases contains 0.75 mol N2, 0.30 mol O2, and 0.15 mol of CO2. If the total pressure of the mixture is
1.56 atm, what is the partial pressure of each component?
0.98 atm nitrogen; 0.39 atm oxygen; 0.20 atm carbon dioxide
28. Place the following gases in order of increasing average molecular speeds at 300 K: CO2, N2O, HF, F2, H2
CO2=N2O < F2<HF <H2
29. Under what conditions of temp. and pressure do gases usually behave nonideally? Low temp and high pressure
30. Would you expect water or carbon dioxide to behave more like an ideal gas at high pressures? Carbon dioxide
31. How do viscosity and surface tension change as intermolecular forces become stronger? More viscose and
higher surface tension
32. How do viscosity and surface tension change as temperature increases? Less viscose and less surface tension
33. Explain why the heat of fusion of any substance is generally lower than its heat of vaporization less bonds are
being broken when melting than vaporizing so it takes less energy
34. Explain how each of the following affects the vapor pressure of a liquid
a. Volume of the liquid
b. surface area c. intermolecular attractive forces
d. temperature
No affect
no affect
higher IMF = lower vapor pressure
higher temp=higher vapor pressure
35. Phosphorus trichloride is more volatile than arsenic trichloride.
a. Which substance has greater intermolecular forces? Arsenic trichloride
b. Which substance as a higher vapor pressure at 25 C? phosphorus trichloride
c. Which substance will have the higher boiling point? Arsenic trichloride
36. Two pans of water are on different burners of a stove. One pan of water is boiling vigorously, while the other is
boiling gently. What can be said about the temperature of the water in the two pans? They are the same
37. Mt. McKinley in Alaska is the tallest peak in the United States. If the barometric pressure at the top is 340 torr,
at what temperature will water boil there? Between 70-80 ⁰C (closer to 80⁰C)
38. As the intermolecular attractive forces between molecules increases, do you expect each of the following to
increase or decrease?
a. Vapor pressure
b. heat of vaporization
c. boiling point
d. freezing point
Decrease
increase
increase
increase
b. Viscosity
f. surface tension
g. critical temperature
Increase
increase
increase
39. First identify the sections where the following phases are found:
a. ____E___ gas
b. __A_____ solid
c. ___C____ liquid
d. ____B___ solid and liquid
e. __D_____ liquid and gas
40. Identify by letter (A-E) in which section the following are found:
a. ___B____ Freezing (if cooling)
b. _____E__ Particles farthest apart
c. ___D____ Boiling
d. __A_____ Particle motion is most restricted
e. ___B____ Heat of fusion
f. ____B,D___ All areas where energy change is potential only
g. ___D____ Heat of vaporization
h. _____B,C,D,E__ All areas where particles move past each other
i. ____A___ Least kinetic energy
j. __A,C,E_____ All areas where kinetic energy is changing
k ___E____ most potential energy
l. _B,D______ All areas where phase changes occur
m. __A,C,E_____ All areas in which the heat is making the particles move faster
n. ___B,D____ All areas in which the heat is breaking the attractions or bonds between particles
o. __B,D_____ All areas in which the particles are not changing their speed
practice FRQ
41. A sample of a pure, gaseous hydrocarbon is introduced into a previously evacuated rigid 1.00 L vessel. The
pressure of the gas is 0.200 atm at a temperature of 127 oC.
a)
Calculate the number of moles of the hydrocarbon in the vessel. 6.09 x 10-3 mol
(1 point earned for showing the setup and a second point earned for correct answer)
b)
O2(g) is introduced into the same vessel containing the hydrocarbon. After the addition of the O2(g), the
total pressure of the gas mixture in the vessel is 1.40 atm at 127 oC. Calculate the partial pressure of
O2(g) in the vessel.
1.40 atom – 0.200 atm = 1.20 atm ( 1 point earned for correct answer)
The mixture of the hydrocarbon and oxygen is sparked so that a complete combustion reaction occurs, producing CO2(g)
and H2O(g). The partial pressures of these gases at 127 oC are 0.600 atm for CO2(g) and 0.800 atm for H2O(g). There is
O2(g) remaining in the container after the reaction is complete.
c)
Use the partial pressures of CO2(g) and H2O(g) to calculate the partial pressure of the O2(g) consumed in
the combustion.
0.0122 mol O2 are used to make water; 0.0183 moles of O2 are used to make CO2 so 0.0305 mol of O2
moles are consumed which has a pressure of 1.00 atm
1 point is earned for the correct stoichiometry in O2 consumption.
1 point is earned for the calculated result.
d)
On the basis of your answers above, write the balanced chemical equation for the combustion reaction
and determine the formula of the hydrocarbon.
0.200 atm : 1.00 atm : 0.600 atm : 0.800 atm
=1:
5:
3:
4
C3H8 + 5 O2  3 CO2 + 4 H2O
1 point is earned for the formula of the hydrocarbon.
1 point is earned for a balanced equation with the correct proportions among reactants and products.
e)
Calculate the mass of the hydrocarbon that was combusted.
(6.09 x 10-3 mol)(44.1 g/mol) = 0.269 g
1 point is earned for using the number of moles combusted from part (a).
1 point is earned for the calculated mass.
42. A sample of C2H4(g) is placed in a previously evacuated, rigid 2.0 L container and heated from 300 K to 450 K. The
pressure of the sample is measured and plotted in the graph below.
a.
Describe TWO reasons why the pressure changes as the temperature of the C2H4(g) increases. Your
descriptions must be in terms of what occurs at the molecular level.
Two reasons are:
(1) As the temperature increases, the average speed of the molecules increases and the
molecules collide more frequently with the container walls.
(2) As the temperature increases, the average kinetic energy of the molecules increases and
the molecules strike the walls of the container with greater force.
Review:
43. Write a balanced net ionic reaction
a. Silver nitrate + sodium phosphate 3Ag+ + PO43-  Ag3PO4
Label all the strong electrolytes silver nitrate, sodium phosphate, sodium nitrate
b. Hydrogen gas + potassium carbonate H2 + K+ + CO32-  CO2 + H2O + K
Label all the nonelectrolytes H2, CO2, H2O
44. How many protons, neutrons, and electrons are in the following
a. 65Zn2+
b. 40Ar
c. 14N3d. 23Na+
30, 35, 28
18, 22, 18
7,7,10
11, 12,10
45. Arrange the following substances according to their expected lattice energies, listed them from lowest lattice
energy to highest: LiCl, KCl, KBr, CaO
KBr, KCl, LiCl, CaO
46. Which member of the following pairs of substances would you expect to have a higher boiling point?
a. N2 or O2
b. NaCl or CH3Cl
c. CH3Cl or CH4
47. Which of the following factors most directly determines the number of peaks in a photoelectron spectrum?
a. The number of electrons
b. The number of shells
c. The number of subshells containing electrons
d. The number of orbitals containing electrons