# Kinetic Molecular Theory and Gas Law Unit Packet

Kinetic Molecular Theory and Gas Law Unit Packet

NAME____________ PERIOD____NUMBER:_____

Kinetic Molecular Theory notes

Before you begin your studies of Kinetic Molecular Theory, you need to know what the word means. Kinetic refers to things in motion; molecular deals with molecules; a theory is a hypothesis that has been supported with experimental evidence. Now, we need to define terms. You know what these terms are, but for the discussion of this unit, we will define them differently than normal.

Temperature is a measure of the average kinetic energy of the molecules in a sample. Since KE = ½ mv2, the change in temperature of a sample is caused by a change in velocity (speed) of the molecules in that sample.

Volume of a sample is the space that the particles take up (not much differently than it is normally thought of).

Pressure of a gas sample is caused by the molecules of that sample colliding with the walls of the container. Pressure = Force / Area, so in order for a gas to exert more pressure on its container, there must be more collisions or more forceful collisions.

Kinetic Molecular Theory is guided by the following assumptions:

1. The molecules of an ideal gas (an ideal gas is a gas that follows the assumptions of kinetic molecular theory) are in constant, random, straight-line motion. Gas molecules are constantly moving very, very fast and their direction is completely random. They move in straight lines within their container.

2. The molecules in an ideal gas can be considered dimensionless points. This assumption can be made because molecules are very, very small compared with the empty space in a gas sample. Therefore, you can assume that the volume of a gas sample is equal to the size of the container that it is held.

3. The collisions between molecules in an ideal gas with each other and the walls of its container are completely elastic. Elastic collisions mean that no energy is lost or gained when the molecules collide.

4. There are no attractive or repulsive forces in an ideal gas. This means that the molecules of an ideal gas do not like or hate each other, they are indifferent. If they pass by another gas molecule, they don’t even notice them, they just go about their

business. This assumption is totally false, but as long as the molecules of the gas have plenty of space, they really won’t interact with each other.

Consequences of KMT (Kinetic Molecular Theory)

When gas molecules follow these rules, the gas is said to be “ideal”. Most gases are ideal and will follow these rules. The only conditions under which these assumptions fail is when the gas sample is either under high pressure or at low temperatures. When a gas is compressed under high pressure, the gas is no longer mostly empty space, so assumption number 2 fails and the gas will condense to a liquid. When a gas is at low temperature, the molecules are moving slowly enough that they notice each other and assumption number 4 fails. Once the gas molecules realize that they are not alone, they start to feel attractive and/or repulsive forces and they will condense to a liquid.

Scientists and Gas Laws

Scientists started to conduct experiments with gases and they came up with equations to describe the relationships between the variables, temperature, volume, pressure, and moles of gas. Once you understand the assumptions of KMT and the definitions of the variables, the relationships make sense. Here are the scientists and their laws:

Boyle’s law – If you hold temperature and the amount of molecules in a gas sample constant, the pressure of a sample of gas is inversely proportional to the volume. In equation form this law is P x V = Constant number.

In English: If the speed of the molecules in a gas doesn’t change (Temperature constant), if you change the amount of space the molecules have, you will change the amount of times they collide with the walls of the container. If you have less space, you have more collisions and vice versa.

Charles’ Law – If you hold the pressure and amount of molecules in a gas sample constant, the volume of a sample of gas is directly proportional to the temperature. In equation form this law is V/T = Constant number.

In English: If the frequency of the molecules collisions with the walls doesn’t change (Pressure constant), a change in the speed of the molecules requires a change in the amount of space they take up. If the molecules move faster, they need more room and vice versa.

Gay-Lussac’s Law – If you hold the volume and amount of molecules in a gas sample constant, the pressure of a sample of gas is directly proportional to the temperature. In equation form this law is P/T = Constant number.

In English: If the amount of space doesn’t change (Volume constant), a change in the speed of the molecules will result in a change in the collisions with the walls of the container. If the molecules move faster, they will hit the walls more often and with more force and vice versa.

Avogadro’s Law – If you hold the temperature and pressure of a gas sample constant, the volume of a gas sample is directly proportional to the number of molecules. In equation form this law is V/n = Constant number.

In English: If the speed of the molecules and the number of collisions with the walls of the container doesn’t change, when you change the amount of molecules, the amount of space they take up will change. If you add more molecules, they take up more space and vice versa.

Can you combine them?

If you combine all of the gas laws together, you get a gas law for all situations, as long as the gas behaves ideally. Strangely, chemists refer to this law as the ideal gas law.

P x V = n x R x T

Pressure times Volume = amount of moles times the Ideal Gas Constant times Kelvin Temperature. The Ideal Gas Constant is located on the back of your periodic table. In fact, a summary of gas laws is located on the back of the periodic table.

R = 0.0821 L atm/mol K OR 8.31 J/mol K

L = Liters, atm = atmospheres, mol = moles, K = Kelvin,

J = Joules = Liters x kilopascals

The key for gas law calculations is to keep the units the same. So, you need to know what the different units for each variable are and how to convert between them.

Pressure

• Atmospheres – this unit is abbreviated (atm) and was invented to be the standard unit for pressure. “Standard pressure” is defined as 1 atmosphere.

• Pascals – this unit is abbreviated (Pa) and is the force of 1 ant doing one push-up. You will see kiloPascals used more often. “Standard pressure” is equal to 101.3 kPa.

• Pounds per square inch – this unit is abbreviated (psi) and is commonly used in the English system. “Standard pressure” is equal to 14.7 psi.

• Barometric height – a barometer is used to measure atmospheric pressure. For a barometer, you measure the height of air supported by a column of mercury. “Standard pressure” is 760 mm Hg or 29.92 inches Hg.

Volume

• Liters – this is pretty much the only unit we will use for volume (L)

Temperature

• Fahrenheit – this is what we use in America, but no one else does. Celsius is more often used. Here’s the equation to convert from Fahrenheit to Celsius: 0C = 5/9(0F – 32)

• Celsius – this is the standard international unit for temperature. If you want to convert from Celsius to Fahrenheit: 0F = 9/50C + 32

• Kelvin – this is the unit you will use for gas law calculations. Kelvin is based on absolute zero, which is the temperature where all molecular motion will theoretically stop. A unit of Kelvin is equal to one degree Celsius, but they have different starting points for the scale. To convert from Celsius to Kelvin: K = 0C + 273.15

So now what to use it for (Sample Gas Law Calculations)

Here are the equations you will use for these problems:

|Boyle’s law: |Charles’ Law: |Gay-Lussac’s Law: |Avogadro’s Law: |

|P1V1 = P2V2 |V1/T1 = V2/T2 |P1/T1 = P2/T2 |V1/n1 = V2/n2 |

|Ideal Gas Law: |Combined Gas Law: |

|PV = nRT |P1V1/T1 = P2V2/T2 |

Use the notes from the KMT packet to fill in the blanks on this worksheet.

1. Temperature is a measure of the ______________ ______________ energy of the molecules in a sample.

2. A gas exerts pressure on its container because the molecules ___________ with the walls. Pressure = ______________ / _______________.

3. According to the assumptions of KMT…

• The molecules of an ideal gas are in _____________, _____________, _______________ - _______________ motion.

• The molecules of an ideal gas can be considered ________________ points because most of the volume of a gas is _____________ space.

• Collisions in an ideal gas are completely _____________.

• There are no attractive or repulsive __________ in an ideal gas.

4. The assumptions of KMT fail under high ____________________ or low _______________.

5. _______________ law relates pressure and volume in an equation.

6. _______________ law relates volume and temperature in an equation.

7. _______________ law relates pressure and temperature in an equation.

8. PV = nRT is referred to as the ____________ gas law.

9. Standard pressure is equal to _________ atmospheres, _________ kPa, ________ psi, ____________ mm Hg, or ____________ in Hg.

10. Standard temperature is equal to ___________ 0C or _________ K.

11. Explain the “Crushing Can” demo by using gas laws.

12. Use a metaphor to explain any of the relationships described by the gas laws.

According to KMT, if 2 different gas molecules were at the same temperature and pressure, but one was large and the other small, who would win in a race?

Boyle’s Law Worksheet

Abbreviations

atm - atmosphere

mm Hg - millimeters of mercury

torr - another name for mm Hg

Pa - Pascal (kPa = kilo Pascal)

K - Kelvin

°C - degrees Celsius

Conversions

K = °C + 273

1 cm3 (cubic centimeter) = 1 mL (milliliter)

1 dm3 (cubic decimeter) = 1 L (liter) = 1000 mL

Standard Conditions

0.00 °C = 273 K

1.00 atm = 760.0 mm Hg = 101.325 kPa = 101,325 Pa

Problems: 1. A gas occupies 12.3 liters at a pressure of 40.0 mm Hg. What is the volume when the pressure is increased to 60.0 mm Hg?

2. If a gas at 25.0 °C occupies 3.60 liters at a pressure of 1.00 atm, what will be its volume at a pressure of 2.50 atm?

3. A gas occupies 1.56 L at 1.00 atm. What will be the volume of this gas if the pressure becomes 3.00 atm?

4. A gas occupies 11.2 liters at 0.860 atm. What is the pressure if the volume becomes 15.0 L?

5. 500.0 mL of a gas is collected at 745.0 mm Hg. What will the volume be at standard pressure?

6. Convert 350.0 mL at 740.0 mm of Hg to its new volume at standard pressure.

7. Convert 338 L at 63.0 atm to its new volume at standard pressure.

Charles’ Law Practice

1. Calculate the decrease in temperature when 2.00 L at 20.0 °C is compressed to 1.00L.

2. 600.0 mL of air is at 20.0 °C. What is the volume at 60.0 °C?

3. A gas occupies 900.0 mL at a temperature of 27.0 °C. What is the volume at 132.0 °C?

4. What change in volume results if 60.0 mL of gas is cooled from 33.0 °C to 5.00 °C?

5. Given 300.0 mL of a gas at 17.0 °C. What is its volume at 10.0 °C?

6. A gas occupies 1.00 L at standard temperature. What is the volume at 333.0 °C?

7. At 27.00 °C a gas has a volume of 6.00 L. What will the volume be at 150.0 °C?

8. At 225.0 °C a gas has a volume of 400.0 mL. What is the volume of this gas at 127.0 °C?

Combined Gas Law Practice

Notes:

1. A gas has a volume of 800.0 mL at minus 23.00 °C and 300.0 torr. What would the volume of the gas be at 227.0 °C and 600.0 torr of pressure?

2. 500.0 liters of a gas are prepared at 700.0 mm Hg and 200.0 °C. The gas is placed into a tank under high pressure. When the tank cools to 20.0 °C, the pressure of the gas is 30.0 atm. What is the volume of the gas?

3. What is the final volume of a 400.0 mL gas sample that is subjected to a temperature change from 22.0 °C to 30.0 °C and a pressure change from 760.0 mm Hg to 360.0 mm Hg?

1. What is the volume of gas at 2.00 atm and 200.0 K if its original volume was 300.0 L at 0.250 atm and 400.0 K.

2. At conditions of 785.0 torr of pressure and 15.0 °C temperature, a gas occupies a volume of 45.5 mL. What will be the volume of the same gas at 745.0 torr and 30.0 °C?

3. A gas occupies a volume of 34.2 mL at a temperature of 15.0 °C and a pressure of 800.0 torr. What will be the volume of this gas at standard conditions?

4. The volume of a gas originally at standard temperature and pressure was recorded as 488.8 mL. What volume would the same gas occupy when subjected to a pressure of 100.0 atm and temperature of minus 245.0 °C?

5. At a pressure of 780.0 mm Hg and 24.2 °C, a certain gas has a volume of 350.0 mL. What will be the volume of this gas under STP

6. If a gas occupies a Volume of 78L, at 234 Kpa and 24 C. Calculate the volume at STP.

7. If a gas exerts a pressure of 456atm., Volume of 345 L at 23C. Calculate volume at 45 Kpa and 45K.

Avogadros Law

V1 = V2 Molar volume: 1 mole = 22.4 L at STP

n1 n2

22.4 L = V2

1 mol n2

STP: Standard T = 0 oC & Standard P =1 atm

1. 50 g of nitrogen (N2) has a volume of ___ liters at STP.

2. What is the volume of 100 g of oxygen (O2) STP?

3. What is the density of carbon dioxide at STP?

4. Which sample represents the smallest number of moles?

a) 1L H2 at STP

b) 1L Argon at STP

c) 1L of H2 at STP

5.Which of the samples would have the same number of particles? (Remember 1 mol has 6.02x 1023 particles in it)

a) 1L He at STP and 1L O2 at STP

b) 2L He at STP and 1L of He at STP

c) 1L He at 27 º C and 760 mm of Hg; and 2L He at STP

6. 11.2 L sample of gas is determined to contain 0.5 moles of nitrogen. At the same temperature and pressure, how many moles of gas would there be in a 20 L sample?

7. Consider the following chemical equation: 2NO2 (g) → N2O4 (g)

If 25 mL of NO2 gas is completely converted to N2O4 gas, under the same conditions, what volume will the N2O4 occupy?

8. What variables must be held constant for Avogadro’s Law to be

true?

9. What would happen to:

V if n is increased?

n if V is increased?

V if n is decreased?

n if V is decreased?

10. A sample of gas occupies 2.00 l with 5.00 moles present.

What would happen to the volume if the number of moles is

increased to 10.0?

11. What happened to the number of moles in a sample that originally

occupied 500 ml with 2.50 moles and then occupied 750 ml?

12. A sample of N2 has 1.70 moles and occupies 3.80 l at 25.0˚C.

A) What volume will it occupy with 2.60 moles?

B) How many moles are in a sample that occupies 1.45 l?

Dalton Law of Partial Pressure

P1 + P2 +…..Pn = Ptotal

Dalton’s Law Worksheet (6.8)

1. A metal tank contains three gases: oxygen, helium, and nitrogen. If the partial pressures of the three gases in the tank are 35 atm of O2, 5 atm of N2, and 25 atm of He, what is the total pressure inside of the tank?

2. Blast furnaces give off many unpleasant and unhealthy gases. If the total air pressure is 0.99 atm, the partial pressure of carbon dioxide is 0.05 atm, and the partial pressure of hydrogen sulfide is 0.02 atm, what is the partial pressure of the remaining air?

3. If the air contains 22% oxygen, what is the partial pressure of oxygen near a blast furnace?

4. A mixture of neon and argon gases exerts a total pressure of 2.39atm. The partial pressure of the neon alone is 1.84atm, what is the partial pressure of the argon?

5. A mixture of Oxygen and Hydrogen occupies a pressure of 101.3kPa. The pressure of Hydrogen is 56kpa. Calculate the pressure of oxygen.

6. What is the total pressure of the gases made up of CO2, and H2 if the partial pressure are 22.3kPa and 112kPa respectively?

7. A mixture of He, Ar, and Ne occupy a pressure of 1760mm of Hg. The partial pressure of He is 56kPa, partial pressure of Ne is 76cm, Ccalculate the partial pressure of Ar.

Dalton’s Law of Partial Pressures

Solve the following problems. Show ALL work including equations and units. Round all answers to the correct number of significant figures.

1. A mixture of oxygen, hydrogen and nitrogen gases exerts a total pressure of 278 kPa. If the partial pressures of the oxygen and the hydrogen are 112 kPa and 101 kPa respectively, what would be the partial pressure exerted by the nitrogen?

2. A mixture of neon and argon gases exerts a total pressure of 2.39 atm. The partial pressure of the neon alone is 1.84 atm, what is the partial pressure of the argon gas in kPa?

3. A 5.0 liter container at 20.0oC has 4 gases pumped in. The total pressure of the gases is 4.80 atm. If the pressure of the first gas is 1.20 atm, and the pressure of the second gas is 0.490 atm, the pressure of the third gas is 0.780 atm, what is the pressure of the fourth gas in atmospheres?

4. 220 mL of oxygen gas was collected over water. The total pressure of oxygen plus water vapor was 745.8 mmHg at 25.0oC. What is the pressure, in mmHg, exerted by only the oxygen gas?

5. Hydrogen gas, H2(g), is collected over water at 20.0oC. The total pressure of hydrogen gas and water vapor is 753 mmHg. What is the pressure, in mmHg, exerted by only the hydrogen gas?

6. 455 mL of oxygen gas was collected over water at a temperature of 85.0oC. The total pressure of the gases is 65.8 kPa. What is the pressure, in kPa, of the dry oxygen gas?

Ideal Gas Law Worksheet

PV = nRT

Use the ideal gas law, “PerV-nRT”, and the universal gas constant R = 0.0821 L*atm

to solve the following problems: K*mol

If pressure is needed in kPa then convert by multiplying by 101.3kPa / 1atm to get

R =8.31 L*kPa / (K*mole)

1) If I have 4 moles of a gas at a pressure of 5.6 atm and a volume of 12 liters, what is the temperature?

2) If I have an unknown quantity of gas at a pressure of 1.2 atm, a volume of 31 liters, and a temperature of 87 0C, how many moles of gas do I have?

3) If I contain 3 moles of gas in a container with a volume of 60 liters and at a temperature of 400 K, what is the pressure inside the container?

4) If I have 7.7 moles of gas at a pressure of 0.09 atm and at a temperature of 56 0C, what is the volume of the container that the gas is in?

5) If I have 17 moles of gas at a temperature of 67 0C, and a volume of 88.89 liters, what is the pressure of the gas?

6) If I have an unknown quantity of gas at a pressure of 0.5 atm, a volume of 25 liters, and a temperature of 300 K, how many moles of gas do I have?

7) If I have 21 moles of gas held at a pressure of 78 atm and a temperature of 900 K, what is the volume of the gas?

8) If I have 1.9 moles of gas held at a pressure of 5 atm and in a container with a volume of 50 liters, what is the temperature of the gas?

9) If I have 2.4 moles of gas held at a temperature of 97 0C and in a container with a volume of 45 liters, what is the pressure of the gas?

10) If I have an unknown quantity of gas held at a temperature of 1195 K in a container with a volume of 25 liters and a pressure of 560 atm, how many moles of gas do I have?

11) If I have 0.275 moles of gas at a temperature of 75 K and a pressure of 1.75 atmospheres, what is the volume of the gas?

12) If I have 72 liters of gas held at a pressure of 3.4 atm and a temperature of 225 K, how many moles of gas do I have?

The Ideal and Combined Gas Laws PV = nRT or P1V1 = P2V2

T1 T2

Use your knowledge of the ideal and combined gas laws to solve the following problems. If it involves moles or grams, it must be PV = nRT

1) If four moles of a gas at a pressure of 5.4 atmospheres have a volume of 120 liters, what is the temperature?

2) If I initially have a gas with a pressure of 84 kPa and a temperature of 350 C and I heat it an additional 230 degrees, what will the new pressure be? Assume the volume of the container is constant.

3) My car has an internal volume of 2600 liters. If the sun heats my car from a temperature of 200 C to a temperature of 550 C, what will the pressure inside my car be? Assume the pressure was initially 760 mm Hg.

4) How many moles of gas are in my car in problem #3?

5) A toy balloon filled with air has an internal pressure of 1.25 atm and a volume of 2.50 L. If I take the balloon to the bottom of the ocean where the pressure is 95 atmospheres, what will the new volume of the balloon be? How many moles of gas does the balloon hold? (Assume T = 285 K)

.

MIXED GAS LAWS WORKSHEET

Directions: Answer each question below. Then write the name of the gas law used to solve each question in the left margin next to each question.

1. A gas occupies 3.5L at 2.5 mm Hg pressure. What is the volume at 10 mm Hg at the same temperature?.875 L

2. A constant volume of oxygen is heated from 100(C to 185(C. The initial pressure is 4.1 atm. What is the final pressure?5.03 atm

3. A sample of 25L of NH3 gas at 10(C is heated at constant pressure until it fills a volume of 50L. What is the new temperature in (C?293 C

4. A certain quantity of argon gas is under 16 torr pressure at 253K in a 12L vessel. How many moles of argon are present?.012 mol

5. An unknown gas weighs 34g and occupies 6.7L at 2 atm and 245K. What is its molecular weight?51.1 g/mol

6. An ideal gas occupies 400ml at 270 mm Hg and 65(C. If the pressure is changed to 1.4 atm and the temperature is increased to 100(C, what is the new volume?110.4 mL or .110 L

7. What is the volume of 23g of neon gas at 1(C and a pressure of 2 atm?12.8 L

8. If 11 moles of HCl gas occupies 15L at 300(C, what is the pressure in torr?

26,220 torr

9. The pressure is 6.5 atm, 2.3 mole of Br2 gas occupies 9.3 L . What is the temperature in (C? 47 C

10. A 600mL balloon is filled with helium at 700mm Hg barometric pressure. The balloon is released and climbs to an altitude where the barometric pressure is 400mm Hg. What will the volume of the balloon be if, during the ascent, the temperature drops from 24 to 5(C? 983 mL or .983 L

11. An unknown gas has a volume of 200L at 5 atm and -140(C. What is its volume at STP? 2052.6 or 2053 L

12. In an autoclave, a constant amount of steam is generated at a constant volume. Under 1.00 atm pressure the steam temperature is 100(C. What pressure setting should be used to obtain a 165(C steam temperature for the sterilization of surgical instruments? 21.22 kPa

13. Determine the total pressure of a gas mixture that contains oxygen, nitrogen and helium in the following partial pressures of 2.0atm for oxygen, 4.7atm for nitrogen and 253.25kPa for helium. 9.2 atm or 931.96 kPa

Gas Laws Study Guide Name: ___________________

Define the following terms as they apply to Kinetic Molecular Theory:

Pressure –

Temperature –

Volume –

n (moles) -

Calculations

1. A gas sample has a volume of 150 mL when the pressure is 175 kPa. If the temperature and amount of gas remains constant, what volume will the gas sample occupy at a pressure of 120 kPa?

2. A 650 mL sample of gas is collected at a room temperature of 300C. What volume will the sample have at 0.00C assuming the pressure of the gas remains constant?

3. An aerosol can of hair spray is filled to a pressure of 50.0 psi at a room temperature of 25.00C. Calculate the pressure inside the can if the can is placed in boiling water.

4. A balloon has a volume of 400.0 mL at a pressure of 600.0 mm Hg. Calculate the volume the balloon would have at standard atmospheric pressure if the temperature remains constant.

5. A car tire has a pressure of 30.0 psi at a temperature of 27.00C. Calculate the extremes of pressure caused by temperatures ranging from –20.00C (-4.000F) on a cold winter day to 50.00C (1220F) while being driven on a hot summer day.

6. A gas sample has a volume of 480 mL at a temperature of 370C and a pressure of 95.5 kPa. What volume would the gas occupy at STP?

7. If you collect 1.75-L of Hydrogen gas during a lab experiment, when the room temperature is 230C and the barometric pressure is 105 kPa, how many moles of hydrogen will you have?

8. What volume of gas would you expect to get from a 1.5-mole sample at 350C and 1.12 atm?

9. A gas contains oxygen, nitrogen, carbon dioxide, and trace amounts of other gases. What is the partial pressure of oxygen (PO2) at 101.3kPa of total pressure if it’s known that the partial pressures of nitrogen, carbon dioxide, and other gases are 79.1kPa, 0.040kPa, and 0.94kPa, respectively? What is the name of the gas law used for this? 21.22 kPa

10. Explain what each of the following changes would do to the pressure in a closed container (increase or decrease pressure). A) Part of the gas is removed, B) The container size (volume) is decreased, and C)Temperature is increased.

A. gas removed ( decrease in pressure

B. Volume decrease ( increase in pressure

C. Temperature increase ( increase in pressure

PRACTICE TEST ON GAS LAWS

Directions: Answer each question below. Then write the name of the gas law used to solve each question in the left margin next to each question.

Show all your work as done in class. Show three steps for each problem. Express your final answer in proper sig figs and proper units; and circle your final answer. Use the ideal gas law, “PV-nRT”, and the universal gas constant R = 0.0821 L.atm/K.moles.

1. A gas occupies 3.5L at 2.5 mm Hg pressure. What is the volume at 10 mm Hg at the same temperature? Formula used_________________ Name of the law_________________

Solve:

2. A sample of 225L of NH3 gas at 15(C is heated at constant pressure until it fills a volume of 54L. What is the new temperature in (C? Formula used______________ Name of the law_________________

Solve

3. A certain quantity of argon gas is under 166 atm pressure at 203K in a 122L vessel. How many moles of argon are present? Formula used______________ Name of the law_________________

Solve

R= 0.0821

4. An unknown gas weighs 234g and occupies 16.7L at 2 atm and 215K. What is its molecular weight? Formula used______________ Name of the law_________________

Solve

5. An ideal gas occupies 408ml at 2170 atm and 65(C. If the pressure is changed to 18.4 atm and the temperature is increased to 135 k, what is the new volume? Formula used______________ Name of the law_________________

Solve

6. An unknown gas has a volume of 245L at 56 atm and -124(C. What is its volume at STP? Formula used______________ Name of the law_________________

Solve

7. Air contains oxygen, nitrogen, carbon dioxide, and trace amounts of other gases. What is the partial pressure of oxygen (PO2) at 101.3kPa of total pressure if it’s known that the partial pressures of nitrogen, carbon dioxide, and other gases are 79.1kPa, 0.040kPa, and 0.94kPa, respectively? Formula used _____________________________Name of the law__________

Solve:

8. What is the ration of rate of diffusion of ammonia gas and carbon dioxide gas at the same temperature?

Formula used _________________________Name of the law_________________

Solve

9. In an experiment, it takes an unknown gas 2.5 times longer to diffuse than the same amount of oxygen gas, O2. Find the molar mass of the unknown gas. Formula used______________________ Name of the law________________

10. Convert 98 atm to Kpa. Formula used_________________

Conceptual Model of gases

In this chapter, we learned that the Kinetic Molecular Theory is related to gas behavior. To understand and predict the behavior of a contained gas in a quantitative manner, we need to recognize that there are only 4 physical properties involved:

1) Quantity of gas: usually expressed as moles, symbol n

2) Volume of gas, which describes , symbol V

3) Temperature of gas, which describes , symbol T

4) Pressure of gas, which describes , symbol P

Consider each of the following situations. Decide how each of the four properties listed above is involved. Indicate as follows: I = increases; D = decreases; C = remains constant or no change.

1. On a very cold day in December, you take a basketball outside to shoot hoops in the driveway. After several minutes the basketball does not bounce as well. For the gas inside the ball, does each property I, D, or C? Has atmospheric pressure changed during this period?

A) quantity B) volume C) temperature D) pressure

2. On a cold autumn morning, a camper’s air mattress seems flatter than it was the afternoon before. Does each property I, D, or C?

A) quantity B) volume C) temperature D) pressure

3. You notice that one of your tires seems a little flat one morning, and decide to fill it with air at a gas station. By the time you get to the gas station it looks fine, and the pressure is normal. What has happened to the air in the tire?

A) quantity B) volume C) temperature D) pressure

4. You buy a bouquet of mylar helium balloons to surprise a friend for her (December) birthday. You leave the balloons in your car overnight and the next day they are soft and deflated. For the helium in the balloons:

A) quantity B) volume C) temperature D) pressure

Is the helium pressure in the “deflated” balloons equal to, less than, or greater than atmospheric pressure?

5. In a cryogenics lab, a scientist takes a small partially-filled balloon out of a canister of liquid nitrogen. As the balloon rests on the table, it grows in size. Evaluate each property for the gas in the balloon.

A) quantity B) volume C) temperature D) pressure

6. A scuba diver has her tank filled at the dive shop one summer morning. She then leaves the tank in the trunk of her car for a few hours. For the gas in the filled scuba tank:

A) quantity B) volume C) temperature D) pressure

7. One of your bike’s tires has a slow leak. For the air inside the tire:

A) quantity B) volume C) temperature D) pressure

If the leak continues, will all the air come out? Explain.

8. A welder uses oxygen for the combustion reaction in his oxyacetylene torch. At the beginning of the work day, the gauge of the tank indicates the pressure of the oxygen is 2250 psi. Evaluate the oxygen at the end of the day:

A) quantity B) volume C) temperature D) pressure

Real-World Examples: answer each in your own words.

1. Why do tire manufacturers recommend that you check the air pressure in your tires before driving the car more than a mile or after letting the car sit for three hours?

2. Why is it dangerous to throw aerosol containers (like hair spray cans) into a fire?

3. The largest container on popcorn on record was 106 m3. There is water vapor (a gas) inside popcorn kernels. Why does adding heat pop the kernel into corn?

4. Liquid nitrogen at a temperature of -47°C is poured onto a balloon, and the balloon shrinks rapidly. Explain what happens to the kinetic energy of the oxygen molecules in the balloon.

5. When you climb a mountain or ride in an elevator to the top of a skyscraper, your ears may “pop.” Explain this.

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