SCH 3U Workbook Answer Key - Unit 4

Francis Libermann Catholic High School Science Department

Grade 11 University Chemistry SCH 3U1 – Course Workbook Unit 4 Answer Keys

name:

date:

States of Matter & the KMT – Understanding Concepts 1. Knowledge: Using the kinetic molecular theory of matter, explain each of the following observations. a.) Gases are more compressible than liquids. ____________________________________________________________________________ ____________________________________________________________________________ b.) The density of gases is less than that of solids. ____________________________________________________________________________ ____________________________________________________________________________ 2. Knowledge: In your own words, describe the characteristics of an ideal gas. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ 3. Application: Using your knowledge of intermolecular forces, predict the state of each substance at room temperature. Explain your answer. a.) hexane (C6H14) ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ b.) hydrogen fluoride (HF) ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ c.) potassium chloride (KCl) ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – States of Matter & the KMT – Science Department

1

name:

date:

4. Thinking: Explain each of the following observations. a.) Metals expand when heated, yet contract in cold weather. ____________________________________________________________________________ ____________________________________________________________________________ b.) Gases have no fixed volume. ____________________________________________________________________________ ____________________________________________________________________________ c.) A certain amount of moles of water occupies much more space as a gas than as a liquid. ____________________________________________________________________________ ____________________________________________________________________________ 5. Communication: How does the degree of disorder of a gas compare to that of a liquid or a solid?

Explain your answer. ____________________________________________________________________________ ____________________________________________________________________________ 6. Knowledge: Describe the motion of a gas particle. ____________________________________________________________________________ ____________________________________________________________________________ 7. Knowledge: What effect does heating have on the particles of a liquid? ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – States of Matter & the KMT – Science Department

2

7. Adding heat increases the kinetic energy of molecules in a liquid, which increases

6. Molecules in gases have vibrational, rotational and translational the vibrational and rotational motion of the molecules, resulting motion. in an increase in

name:

date:

With enough energy, they canof break the intermolecular and 7. Addingvolume. heat increases the kinetic energy molecules in a liquid,attractions which increases become a gas.

and Draw rotational motion ofnotebook. the molecules, resulting increase Communication: 8.thea.)vibrational five boxes in your Inside them, illustratein thean motion of gasin 8. (a) Note that it will be difficult for students to not draw attractive forces as in or to particlesWith according to theenergy, kinetic molecular volume. enough they cantheory. break the intermolecular attractions ii) and show a difference in temperature in just one box as in v)

become a gas. (i) Volume of gas (ii) Neither (iii) Molecules in (iv) Gas molecules (v) With 8. (a) Note that it will be difficult for students to not draw attractive forces as in ii) or to molecules is attractive or gases have have elastic increasing show a difference inrepulsive temperature inhigh justenergy one box as collisions. in v) small temperatures compared to

forces

(i) Volume the of gas space (ii) Neither between

molecules is them. attractive or between molecules. small repulsive compared to forces the space between between them. molecules.

and move in all

(iii) Molecules directionsinin

gases have straight lines. high energy and move in all directions in straight lines.

(iv) Gas molecules

have elastic collisions.

the kinetic

(v)energy Withof the

increasing molecules increases. temperatures the kinetic energy of the molecules increases.

(b) Students’ answers may not be exactly like the drawings.

b.) Draw another five boxes underneath the five boxes in (a). Illustrate how you think the molecules of a real gas might move in comparison.

(b) Students’ answers may not be exactly like the drawings.

HR • Unit 4 Gases and Atmospheric Chemistry

Gases and Atmospheric Chemistry

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – States of Matter & the KMT – Science Department

3

name:

date:

Gas Pressure and Volume – Practice Problems KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

1. A 50.0 cm3 sample of nitrogen gas is collected at 101.3 kPa. If the volume is reduced to 5.0 cm3, and the temperature remains constant, what will the final pressure of the nitrogen be?

2. A weather balloon has a volume of 1.00×103 L at a pressure of 740.0 torr. The balloon rises to a height of 1.00×103 m where the atmospheric pressure is measured as 450.0 torr. Assuming there is no change in temperature, what is the final volume of the weather balloon?

3. A 45.0 cm3 sample of nitrogen gas is collected at 1.0 atm. The nitrogen is compressed to a pressure of 10.0 atm. What is the final volume of the nitrogen if the temperature remains constant?

4. A 45.6 mL sample of gas at 490 torr is compressed to a certain volume at 3.0 atm. What is the new volume, in litres?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Practice Questions – Science Department

1

name:

date:

5. Using the relationship 760 mm Hg = 760 torr = 1 atm = 101.3 kPa, convert each of the following units: a.) 2.03 atm to kPa b.) 85.2 kPa to atm

c.) 1.50 atm to torr

d.) 6.0×102 torr to kPa

6. Use the kinetic molecular theory. Explain why the air pressure inside a capped syringe increases if the volume decreases from 15 cm3 to 10.0 cm3.

7. Explain, using the kinetic molecular theory, why pressure is exerted by gases in all directions.

8. A 1.00 L helium balloon is floating in the air on a day when the atmospheric pressure is 102.5 kPa and the temperature is 20.0°C. Suddenly, clouds appear and the pressure rapidly drops to 98.6 kPa at a temperature of 20.0°C. What is the new volume of the balloon?

9. 0.750 L of oxygen gas is trapped at 101.3 kPa in a cylinder with a moveable piston. The piston is moved and the gas is compressed to a volume of 0.500 L. What is the final pressure applied to the oxygen gas if the temperature remains unchanged?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Practice Questions – Science Department

2

name:

date:

Gases and Temperature Changes – Practice Problems KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

1. Convert the following temperatures to the Kelvin scale. a.) 25°C

2.

b.) 37°C

c.) 150°C

Convert the following temperatures to degrees Celcius. a.) 373 K b.) 98 K

c.) 425 K

3.

A sample of nitrogen gas surrounding a circuit board occupies a volume of 300.0 mL at 17°C and 100.0 kPa. What volume will the nitrogen occupy at 100.0°C if the pressure remains constant?

4.

A 2.5 L balloon is completely filled with helium indoors at a temperature of 24.2°C. The balloon is taken out on a cold winter day (–17.5°C). What will the volume of the balloon become, assuming a constant pressure?

5.

10.0 L of neon at 20.0°C is expanded to a volume of 30.0 L. If the pressure remains constant, what must the final temperature be (in °C)?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Practice Questions – Science Department

1

name:

date:

6.

A 14.5 cm3 sample of oxygen gas at 24.3°C is drawn into a syringe with a maximum volume of 60.0 cm3. What is the maximum change in temperature that the oxygen can be subjected to before the plunger pops out of the syringe?

7.

Methane gas can be condensed by cooling and increasing the pressure. A 600.0 L sample of methane gas at 25°C and 100.0 kPa is cooled to !20.0°C. In a second step, the gas is compressed until the pressure is quadrupled. What will the final volume be? (Hint: Use both Boyle’s law and Charles’ law to answer this question.)

8.

An unknown gas is collected in a 250.0 mL flask and sealed. Using electronic devices, it is found that the gas inside the flask exerts a pressure of 135.5 kPa at 15°C. What pressure will the gas exert if the temperature (in Kelvins) is doubled?

9.

At 18°C, a sample of helium gas stored in a metal cylinder exerts a pressure of 17.5 atm. What will the pressure become if the tank is placed in a closed room where the temperature increases to 40.0°C?

10. A gaseous refrigerant, enclosed in copper tubes, surrounds the freezer in a small refrigerator. The gas is found to exert a pressure of 110 kPa at 45°C. The refrigerant is allowed to expand through a nozzle into an expansion chamber such that the exerted pressure decreases to 89 kPa. What is the temperature inside the freezer?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Practice Questions – Science Department

2

name:

date:

Gases and Temperature Changes – Key Concepts KNOWLEDGE 1.

THINKING

COMMUNICATION

APPLICATION

What safety concerns and precautions should be taken with compressed gases? Use what you know about the movement of particles to explain these precautions. __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________

2.

a.) A gas at 107 kPa and 300.0 K is cooled to 146 K at the same volume. What is the new pressure?

b.) 17 L of gas at 300.0 K are cooled to 146 K at the same pressure. What is the new volume?

3.

Describe the relationship between your answers in parts (a) and (b) of question 2. __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________

4.

Explain in terms of molecular motion why, when the temperature is increased: a.) a gas increases in volume __________________________________________________________________________________________ __________________________________________________________________________________________ b.) the pressure of a gas increases __________________________________________________________________________________________ __________________________________________________________________________________________

5.

A balloon at a party drifts above a hot stove, and explodes. Why did this happen? __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________

KNOWLEDGE

THINKING

COMMUNICATION 1

APPLICATION

FRANCIS LIBERMANNCATHOLICHIGHSCHOOL Chemistry Unit – Practice Questions – Science Department

name:

date:

Combined Gas Law – Practice Problems KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

1.

A sample of gas has a volume of 150 mL at 260 K and 92.3 kPa. What will the new volume be at 376 K and 123 kPa?

2.

A cylinder at 48 atm pressure and 290 K releases 35 mL of carbon dioxide gas into a 4.0 L container at 297 K. What is the pressure inside the container?

3.

In a large syringe, 48 mL of ammonia gas at STP is compressed to 24 mL and 110 kPa. What must the new temperature of the gas be?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Combined Gas Laws – Science Department

1

name:

date:

4.

A 100 W light bulb has a volume of 180.0 cm3 at STP. The light bulb is turned on and the heated glass expands slightly, changing the volume of the bulb to 181.5 cm3 with an internal pressure of 214.5 kPa. What is the temperature of the light bulb (in °C)?

5.

Sulfur hexafluoride, SF6(g) , is used as a chemical insulator. A 5.0 L sample of this gas is collected at 205.0°C and 350 kPa. What pressure must be applied to this gas sample to reduce its volume to 1.7 L at 25°C?

6.

To speed up a reaction in a vessel pressurized at 98.0 kPa, a chemist added 202.65 kPa of hydrogen gas. What was the resulting pressure?

7.

A gas mixture contains 12% Ne, 23% He, and 65% Rn. If the total pressure is 116 kPa, what is the partial pressure of each gas?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Combined Gas Laws – Science Department

2

name:

date:

8.

The partial pressure of argon gas, making up 40% of a mixture, is 325 torr. What is the total pressure of the mixture in kPa?

9.

A mixture of nitrogen and carbon dioxide gas is at a pressure of 1.00 atm and a temperature of 278 K. If 30% of the mixture is nitrogen, what is the partial pressure of the carbon dioxide?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Combined Gas Laws – Science Department

3

name:

date:

Combined Gas Law Calculations – Key Concepts 1. Knowledge: In a large syringe, 48 mL of ammonia gas at STP is compressed to 24 mL and 110 kPa. What must the new temperature of the gas be? Explain the result in terms of kinetic molecular theory.

2. Thinking: Design an investigation to test Dalton’s law of partial pressure. Write a procedure and list the materials and equipment you need. __________________________________________________________________________________________ __________________________________________________________________________________________

3. Communication: Explain Dalton’s law of partial pressure. __________________________________________________________________________________________ __________________________________________________________________________________________

4. Knowledge: What are the main components of the atmosphere? __________________________________________________________________________________________ __________________________________________________________________________________________

5. Application Popcorn pops as the water in the kernel is vapourized. The building pressure becomes too much for the shell of the kernel, and it explodes. Explain, using your knowledge of the behaviour of gases, what happens to the temperature just before and just after the kernel pops. (Use a diagram to help you to visualize the situation.)

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Combined Gas Law Calculations – Science Department

1

name:

date:

Ideal Gas Law – Understanding Concepts 1. Thinking: How many grams of sulfur dioxide are in 36.2 L at STP?

2. Thinking: At certain conditions, 20.0 mol of a gas occupy 498 L. What volume do 35.0 mol occupy?

3. Thinking: What is the pressure of 0.76 mol of gas at 48 ̊C in 8.0 L?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Ideal Gas Law – Science Department

1

name:

date:

4. Thinking: How many grams of bromine gas, Br2, are in 3.12 L at a pressure of 2.4 atm and a temperature of –20.0 ̊C? How many molecules of bromine gas are there?

5. Thinking: What is the temperature of 6.02 mol of hydrogen sulfide in a 132 L tank at 0.95 atm?

6. Knowledge: What was Avogadro’s hypothesis? Explain how Avogadro contributed to our understanding of gases and the relationships among the properties of gases. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Ideal Gas Law – Science Department

2

name:

P B = P total = 1.0 atm nB = 0.60 mol

P A = P total = 0.50 atm nA = 0.30 mol

P total = P A + P B = 1.5 atm n total = 0.90 mol XA = 0.33 mol to one eighth of the XB = 0.67 mol

date:

Knowledge 1.00 m3 of regular air at 1.0 atm 7. A B is compressed constant temperature. What is the pressure contribution of the nitrogen?

When gas A is added to gas B, the total pressure exerted is now 1.5 atm while the volume of the flask remains the same.

volume at a

Table 11.2 Components of the Dry Atmosphere Components

The action of winds mixes the atmosphere so that the composition of the dry atmosphere is fairly constant over the entire Earth. Water vapour, though an important component of the atmosphere, is not listed in the table. The quantity of water vapour in the air, or humidity, is variable. In desert climates, the quantity of water vapour will be very small (low humidity). In tropical areas, or near large bodies of water, the quantity of water vapour in the air can be quite substantial (high humidity).

Percentage

Nitrogen (N2)

78.08

Oxygen (O2)

20.95

Argon (Ar)

0.93

Carbon dioxide (CO2)

0.03

Neon (Ne)

0.002

Other gases

0.008

Dalton extended this idea to enhance what he had discovered about the composition of the atmosphere. If the atmosphere is 79% nitrogen, and the atmospheric pressure on a certain day is, for example, 101.3 kPa, then he concluded that the nitrogen itself must be contributing 79 " 101.3 kPa = 80 kPa 100 The other gases in the atmosphere contribute pressures corresponding to their percentage of the total composition of air.

The generalized form of Dalton’s law of partial pressures is Ptotal = P1 + P2 + P3 + . . . + Pn This law can be applied to any mixture of gases. Study the following Sample Problem and try the Practice Problems to verify your understanding of how Dalton’s law works.

Chapter 11 The Behaviour of Gases • MHR

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Ideal Gas Law – Science Department

3

459

name:

date:

Application of the Ideal Gas Laws – Understanding Concepts 1. Thinking: What is the density of methane, CH4(g), if 4.5 mol are in 100.0 L?

2. Thinking: 8.1g of a gas occupy 12.3L of space at 27 ̊C and 8.0 atm. a.) What is the molar mass of the gas?

b.) What might the gas be?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Applications of the Ideal Gas Law – Science Department

1

name:

date:

3. Thinking: A gas that consists of only nitrogen and oxygen atoms is found to contain 30.0% nitrogen.

A 9.23 g sample of the gas occupies 2.2 L at STP. What is the gas?

4. Thinking: You are given a sample of an unknown gas. Describe how you can identify the gas in the laboratory. What measurements will you take? What apparatus might you need? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 5. Knowledge: How can the densities of two gases at STP be different, even though their volumes are the same? _______________________________________________________________________________ _______________________________________________________________________________

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Applications of the Ideal Gas Law – Science Department

2

name:

date:

Gas Law Stoichiometry – Understanding Concepts 1. Knowledge: Gay-Lussac’s law of combining volumes provides a short-cut for some gas calculations. What type of gas reaction lets you use this law? _______________________________________________________________________________ _______________________________________________________________________________ 2. Knowledge: What values should you measure in the laboratory in order to calculate the molar volume of a gas? _______________________________________________________________________________ _______________________________________________________________________________ 3. Communication: Why is it necessary to correct the pressure of a gas that is collected over water?

How would you do this? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 4. Knowledge: Which will occupy a greater volume: 2.0 mol of nitrogen gas at STP or 1.9 mol of oxygen gas at SATP? Explain.

5. Thinking: 2.0 L of hydrogen gas reacts with oxygen at 5.0 ̊C and 99 kPa. How many litres of water vapour are produced?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Gas Law Stoichiometry – Science Department

1

name:

date:

6. Thinking: 13 g of lead reacts with hydrofluoric acid to produce hydrogen gas at 22 ̊C and 88.3 kPa. a.) Describe the apparatus you would need to carry out this reaction in the laboratory. ____________________________________________________________________________ ____________________________________________________________________________ b.) How many litres of dry hydrogen gas are collected?

7. Thinking: Plants consume carbon dioxide gas as they produce sugar during photosynthesis. To produce 50.0 g of sugar, how many litres of gas at SATP does a sugar beet need to consume?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Gas Law Stoichiometry – Science Department

2

name:

date:

8. Thinking: 28L of oxygen gas reacts with 52L of hydrogen gas in an 80.0L vessel at 25 ̊C and 3.0 atm. a.) How many grams of water are produced?

b.) What will the pressure be in the cylinder after the reaction if all of the water that is formed condenses and is removed?

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Gas Law Stoichiometry – Science Department

3

name:

date:

Gas Stoichiometry – Problems KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

Thinking 1. Mole:Volume: What volume of hydrogen would be required to produce 0.400 mole of HCl at 35°C and 0.965 atm? ____ H2(g) + ____ Cl2 (g) → ____ HCl(g) a.) Balance the above equation b.) Using the moles of HCl(g) , determine the mol of H2(g) required.

c.) Convert moles of H2 (g) to volume using the Ideal Gas Law

2. Volume:Volume: What volume of nitrogen at 215°C and 4.56 atm would be required to produce 55 L of ammonia? ____ N2(g) + ____ H2 (g)→ ____ NH3(g) a.) Balance the above equation Since the conditions of temperature and pressure are not changing, use the balanced equation to determine a volume:volume ratio between NH3 (g) and N2 (g).

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Gas Stoichiometry – Science Department

1

name:

date:

3. Mass:Volume: When 10.7 g of Al are reacted with excess HCl, what volume of HCl will be produced at 47°C and 725 mm Hg? ____ Al(s) + ____ HCl(aq) → ____ AlCl3(aq) + ____ H2 (g) a.) Balance the above equation b.) Convert grams of Al to moles.

c.) Convert moles of Al to moles of H2.

d.) Convert moles of H2 to volume using the reaction conditions and the ideal gas law.

KNOWLEDGE

THINKING

COMMUNICATION

APPLICATION

FRANCIS LIBERMANN CATHOLIC HIGH SCHOOL Chemistry Unit – Gas Stoichiometry – Science Department

2