Unit 6 – the Mole and Gas Laws

Unit 6 – The Mole and Gas Laws

Calculating Formula, Atomic, and Molecular Masses (MOLAR MASS)

As you know, the mass of an element on the periodic table is a weighted average of all the naturally- occurring isotopes of that element. Originally, we said that the unit for the mass of an element was ______. From now on, we will be substituting ______as the unit for the mass of an element or compound.

Steps for calculating MOLAR MASS:

1. Write the ______.

2. Calculate the mass by adding up the masses of each element in the compound. If you have more than one of an element, multiply how many you have by its mass before you add. 3. Make the unit ______.

Substance Type of Particle g/mol from Periodic Table FM, AM, or MM?

1) K

2) KCl

3) SO2

4) Ca3(PO4)2

5) (NH4)2CO3

FM: ______AM: ______

MM: ______ Different names for different types of particles, same method of determination

Percent Composition Percent composition refers to what percent of the compound is made up of each element. To calculate the percent composition, divide the mass of the element by the molar mass of the compound. If there is more than one atom of an element, you must multiply the molar mass by the number of moles.

Ex: An 8.40 g sample of fluorine completely combines with a 4.90 g sample of sodium. Calculate the percent composition of the compound that forms.

Ex: Calculate the % composition of copper (II) sulfate. 1) Cu

2) %Cu

% S

% O

Ex: Given 5.0 g of CuSO4, what is the mass of sulfur in the compound?

EX: Given 3629 g of CuSO4, what mass of oxygen is in this compound?

The Mole • One mole is defined as the number of atoms in 12 g of ______. • A mole is a counting number. One mole is a specific number of atoms, molecules, or formula units. A mole is ALWAYS ______. This number was discovered by a scientist named ______. So we chemists call this number Avogadro’s Number. • Now we can relate the atomic mass unit to the gram. 1 atom of carbon-12 has a mass of 12.01 amu (atomic mass unit). Avogadro figured out that 6.02x1023 atoms of carbon-12 have a mass of 12.01 g, therefore, 1 mole of carbon atoms have a mass of 12.01 g. This is why we are now using g/mol as our unit for MOLAR mass.

The Mole has 3 mathematical definitions: 1) 1 mol = ______Where a “particle” can be a ______, ______, ______, or ______

2) 1 mol = ______FOR GAS MOLECULES ONLY

3) 1 mol = ______(3 different types already discussed above)

One-Step Conversions Use the road map to help you convert between one unit of a chemical quantity to another unit. This is set up like a metric conversion! Remember, the mathematical definitions (above) can be written as a fraction for use in a conversion. Ex: Convert 4.3 g of NaCl to moles. Given: Unk: Road map: Work:

Ex: Convert 0.00563 mol NH3to grams. Given: Unk: Road map: Work:

Ex: Convert 3.0x1014 atoms of barium to moles. Given: Unk: Road map: Work:

Ex: Convert 0.156 mol of carbon dioxide gas to molecules of carbon dioxide. Given: Unk: Road map: Work:

Ex: Convert 0.53 L of NO2 gas to mol of NO2 gas. Given: Unk: Road map: Work:

Ex: Convert 2.3 mol of hydrogen gas to L. Given: Unk: Road map: Work:

Two steps Mole Conversion The mole is the link between grams, the number of representative particles and liters. You are familiar with conversions between moles and grams, moles and molecules, and moles and particles.

The Mole Conversion Road Map

• To convert from one unit to another, you must use the mole as an intermediate step. • In other words, you might need a “two-step” conversion problem. • What is a two-step conversion problem? • One to convert from the units you are given to moles. • One to convert from moles to the units you want. Example: Calculate the number of molecules in 60.0 g NO2. Given: 60.0 g NO2 1st Step: State what is known, your unknown and your directions

Given: 60.0 g NO2 Unknown: Molecules of NO2 Road map: grams molecules (no direct path so must convert to moles first)

So grams moles molecules 2nd Step: Calculate Molar Mass

Molar Mass NO2: [N = 14.01 + O = (2) 16.00] so Molar Mass of NO2 = 46.01 g 46.01 g = 1 mole 3rd Step: Set up Equation

23 So here’s the equation: 60.0 g NO2 X 1 mol X 6.02 x 10 molecules = 1 46.01 g NO2 1 mol

23 7.85 x 10 molecules NO2

You will NOT be allowed to use your “Road Map” on the test, so you need to practice enough that you no longer rely on it to help you through solving these problems.

Two-Step Conversions *** Use and make road maps!!! Ex: How many grams are in 5.631 x 1021 atoms Na? Given: 5.631 x 1021 atoms Na Unknown: g Na Road map: Work:

22 Ex: What is the mass of 1.5 x 10 f.u. Ca(OH)2? 22 Given: 1.5 x 10 f.u. Ca(OH)2 Unknown: mass Ca(OH)2 Road map: Work:

Ex: What is the mass of 2.63 L O2?

Given: 2.63 L O2 Unknown: mass O2 Road map: Work:

Ex: What are the formula units for 92.1 g Na2SO4?

Given: 92.1 g Na2SO4 Unknown: formula units (f.u.) Na2SO4 Road map: Work:

-3 Ex: How many molecules are in 6.3 x 10 L SO2 gas? -3 Given: 6.3 x 10 L SO2 gas Unk: mlcs SO2 Road map: Work:

Hydrated Compounds A hydrated compound is a compound with ______molecules attached ______to the ionic crystalline structure. Examples:

CuSO4 • 5H2O ______Calcium sulfate dihydrate ______

BaCl2·• 9H2O ______ Water molecules can be removed by ______the compound. This is not ______, therefore not a ______change. It is a ______reaction. Finding the percent composition of Hydrates: The steps are the same as before, but KEEP ALL WATER MOLECULES TOGETHER! DON’T COUNT O’S AND H’S SEPARATELY! Ex: Lead (II) nitrate trihydrate -count atoms Pb

H2O

-calculate % % Pb

% N

% O

% H2O

Ex: Given a 40 g sample of Pb(NO3)2 • 3H2O, calculate the mass of water present.

Ex: Given a 100 g sample of Pb(NO3)2·• 3H2O, calculate the mass of water present.

Ex: Calculate the % of IONIC COMPD and the % WATER in strontium chloride hexahydrate. Formula:

IONIC WATER

Ex: Calculate the mass of water and the mass of strontium chloride in a 0.500 g sample of SrCl2·• 6H2O

SrCl2:

H2O:

Determining Empirical Formulas An empirical formula (EF) is the ______whole number ______of elements in a compound. Rules: 1) From a given ______or from the ______of each element in the compound, 2) Find ______of each element in the compound. Find ______of water if compound is ______. 3) ______# of moles to get a whole number 4) ______if necessary (mass  mol  / small  x by whole) Ex: Calculate the EF (empirical formula) of a compound containing 25.9 % H and 74.1 % O.

(big hint for EF/MF calculations – carry decimal places way out, like to 0.001 or 0.0001, throughout each step of the process, round at the end)

Ex: Determine the EF for a compound containing 36.5 g Na, 25.4 g S, and 38.1 g O.

Determining Molecular Formulas

A molecular formula (MF) is not necessarily the simplest whole # ratio between atoms. The MF shows the ______number of atoms in a compound.

You will need: 1. ______

2. ______

Ex: Determine the molecular formula (MF) of a compound whose empirical formula is CH2O and the molecular mass is 120 grams per mol. 1)

This tells you how many of each atom are in the compound.

Ex: Methyl butanoate is a compound that smells like apples (used for artificial flavoring). Its % composition is 58.8 % C, 9.8 % H, and 31.4 % O. Its molecular mass is 102 grams per mole. Determine the molecular formula of this compound. 1) Find EF (4 step process, carry decimal places way out)

2) Get Empirical Mass

3) Multiple =

4) MF:

Gas Laws Items to KNOW • STP = Standard Temperature and Pressure (0.00 °C = 273 K and 1 atm) • Standard Temperature = • 1.00 atm = 101.3 kPa = 760 mmHg = 760 torr Abbreviations atm - atmosphere • ⁰C + 273 = K mm Hg - millimeters of mercury Gas Variables and Definitions: torr - another name for mm Hg Pa - Pascal (kPa = kilo Pascal) • Pressure (P) – K - Kelvin °C - degrees Celsius • Temperature (T) –

• Volume (V) –

• Moles (n)

Equations Representing Relationships:

Law Formula

Pressure and Kinetic Molecular Theory Notes What is pressure? 퐹표푟푐푒 푃푟푒푠푠푢푟푒 = 퐴푟푒푎 What is force? You can think of it like weight or like a push. How much does your body push on the floor? How much do you have to push to move something across the floor? Liquids and solids exert pressure. Ex: Diving, your body is under more pressure when under water than when above it. If you are trapped under a piece of furniture you feel the pressure of the furniture on you. What does area have to do with it? Could you sleep on a bed of nails? How about just one nail? Carpenters…why are screws pointy at the end instead of flat? The same force over a smaller area results in a higher pressure.

Gas pressure is similar but hard to visualize. KINETIC MOLECULAR THEORY 1. Gases have a very small ______2. Gases are constantly in ______at high speeds in random but ______line paths 3. Gases experience no ______attractions between ______a. All collisions between particles in a gas are perfectly ______. i. No attractive or repulsive forces ii. No transfer of Kinetic Energy iii. The average Kinetic Energy is dependent only on ______4. The speed of a gas molecule is directly ______to its mass and speed. a. As the temperature increases, the speed of the gas molecule ______.

These assumptions are good for IDEAL gases and are used quite often with little error. However, when one needs to be exact that you must account for the fact that REAL gases • Have volume • Experience electrostatic attractions For Introductory Chemistry, though, we will just deal with Ideal gases.

Pressure is the sum of all the forces of all the gas molecules colliding with a surface. Gas particles are in ______,______, ______; exerting pressure as they collide with the walls of the container. Therefore, the ______collisions, the ______the pressure.

Gases have certain properties that can be explained by the KMT. 1. Low Density they ______because the molecules are moving at a high rate of speed and are not held back by electrostatic attractions as well as being spread out, they have low density. 2. Compressibility, they can be ______to compress because the molecules have space between them, unlike liquids and solids where there is little space between the molecules 3. Expansion, they will ______given the opportunity because the molecules are moving at a high rate of speed. 4. ______they will spread out, again because the molecules are moving at a high rate of speed, a. Example: perfume diffusing through air b. Example: Liquids also diffuse: food coloring in water

5. ______molecules moving at a high rate of speed will eventually “collide” with a hole and escape. a. Effusion is gas escaping through a hole, b. Example: air escaping through a hole in your tire

6. The word kinetic comes from a Greek word that means “to move.” The kinetic molecular theory is based upon the assumption that particles of matter (atoms or molecules) are in constant 7. Of the three states of matter, which one has the most kinetic energy?

8. Which state of matter has particles that are separated by the largest distance?

9. A scientific theory is an explanation of some type of natural phenomena. Theories are normally developed from careful study of the way the world behaves. Let’s look at how gases behave and see if the kinetic molecular theory makes sense. 10. Compared to liquids and solids, gases tend to have ______densities. This can be explained because the particles of gas are ______.

Gas Laws Problems

Steps to Solve any Gas Law Problem: o Step 1: Write everything you are given in the problem. o Step 2: Which law do you want to use? (What remains constant?) o Step 3: Do your units match? If not, convert. (Temperature must always be in Kelvin) o Step 4: Plug in your values and solve. Proportional Indirectly

Boyle's Law Charles Law Gay-Lussac's Law

Dalton’s Law of Partial Pressures

• Boyle's Law o As the pressure decreases, the volume increases. o Indirectly proportional o Temperature remains constant

Example Problem: A balloon contains 30.0 L of helium gas at 1 atmosphere, and it rises to an altitude where the pressure is only 0.25 atm, assuming the temperature remains constant, what is the volume of the balloon at its new pressure?

• Charles' Law

o Lower temperature leads to a lower volume o Higher temperature leads to a higher volume o Directly proportional o Temperature must be converted to Kelvin o Pressure remains constant Example Problem: A balloon inflated in a room at 24OC has a volume of 4.00 L. The balloon is then heated to a temperature of 58OC what is the new volume if the pressure remains constant?

• Gay-Lussac's Law

o Temperature always in Kelvin Scale o Volume remains constant Example Problem: Aeresol cans carry labels warning not to store them above a certain temperature. The gas in a used aerosol can is at a pressure of 1atm at 25oC. If the can is thrown into a fire, what will the pressure be when the temperature reaches 1201oC?

• The Combined Gas Law

o No variable remains constant o Temperature always in Kelvin Scale Example Problem: The volume of a gas filled balloon is 30.0L at 313 K and has a pressure of 153 kPa. What would the volume be at standard temperature and pressure (STP)?

• Dalton’s Law of Partial Pressures

Dalton’s Law of Partial Pressures In a ______of gases, the ______pressure exerted by the mixture of gases is equal to the ______of the partial pressure of each gas.

Example – Air contains N2, O2, H2O, Ar, CO2, the sum of which makes up the air pressure around us at any time.

PTotal = P Gas 1 + P Gas 2 + P Gas3 …

What is the air pressure at sea level if N2, O2, H2O, Ar, CO2, have the following pressures 78.1 kPa + 20.9kPa + 1.28kPa + 0.97kPa + 0.05kPa ?

The Ideal Gas Law The pressure _____, volume _____, and temperature _____ of an ideal gas are related by a simple formula called the ______. The simplicity of this relationship is a big reason why we typically treat gases as ideal, unless there is a good reason to do otherwise. ______Where _____ is the pressure of the gas, _____ is the volume taken up by the gas, _____ is the temperature of the gas, ______, and _____ is the number of ______of the gas. (The most confusing thing about using the ideal gas law is making sure we use the right units when plugging in the gas constant numbers). Gas Constant Units PV=nRT R=______R=______Pressure in Papascals Pa Pressure in atmospheres atm Volume in m 3 volume in Liters L Temperature in kelvin K Temperature in kelvin K Sample Problem

How many moles of H2 is in a 3.1 L sample of H2 measured at 300 kPa and 20°C?

Gas Laws Practice:

1) A chemist collects 59.0 mL of sulfur dioxide gas on a day when the atmospheric pressure is 0.989 atm. On the next day, the pressure has changed to 0.967 atm. What will the volume of the SO2 gas on the second day?

2) A can contains a gas with a volume of 56 mL and 20.0 °C. What is the volume in the can if it is heated to 50.0 °C?

3) A gas with a volume of 4.0L at a pressure of 90.0 kPa is allowed to expand until the pressure drops to 20.0 kPa. What is the new volume?

4) At a winter carnival, a balloon is filled with 5.00 L of helium at a temperature of 273 K. What will be the volume of the balloon when it is brought into a warm house at 295 K?

5) The initial temperature of a 1.00 liter sample of argon is 20.0° C. The pressure is decreased from 720 mm Hg to 360 mm Hg and the volume increases to 2.14 liters. What was the change in temperature of the argon?

6) 2.2 L of hydrogen at 6.5 atm pressure is used to fill a balloon at a final pressure of 1.15 atm. What is its final volume?

7) The pressure in an automobile tire is 200. kPa at a temperature of 25°C. At the end of a journey on a hot sunny day the pressure has risen to 223 kPa. What is the temperature of the air in the tire?

8) A sample of argon has a volume of 5.00 L and the pressure is 0.920 atm. If the final temperature is 30.0° C, the final volume is 5.7 L, and the final pressure is 800. mm Hg, what was the initial temperature of the argon?

9) How many moles of CO2(g) is in a 5.6 L sample of CO2 measured at STP?

Gas Law Practice - Worksheet

1. Why does air come out of a bicycle tire when you open the valve, even if the valve is pointing up?

2. Why do aerosol cans come with the warning, “Contents under pressure. Do not heat.”?

Dalton’s Law Worksheet

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?

Charles’ Law Worksheet

1) The temperature inside my refrigerator is about 40 Celsius. If I place a balloon in my fridge that initially has a temperature of 220 C and a volume of 0.5 liters, what will be the volume of the balloon when it is fully cooled by my refrigerator?

2) A man heats a balloon in the oven. If the balloon initially has a volume of 0.4 liters and a temperature of 20 0C, what will the volume of the balloon be after he heats it to a temperature of 250 0C?

Combined Gas Law Problems

1) If I initially have a gas at a pressure of 12 atm, a volume of 23 liters, and a temperature of 200 K, and then I raise the pressure to 14 atm and increase the temperature to 300 K, what is the new volume of the gas?

2) A gas takes up a volume of 17 liters, has a pressure of 2.3 atm, and a temperature of 299 K. If I raise the temperature to 350 K and lower the pressure to 1.5 atm, what is the new volume of the gas?

Boyle’s Law

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?

Ideal Gas Law and Dalton’s Law Worksheet

1) The air in a person’s lungs consists of 0.177 mol of gas particles at 310 K and 101.3 kPa pressure. What is the volume of the air?

2) How many moles of gas are contained in 22.41 liters at 101.325 kPa and 0°C?

3) How many moles of gases are contained in a can with a volume of 555 mL and a pressure of 600.0 atm at 20 °C?

4) Calculate the pressure exerted by 43 mol of nitrogen in a 65 L cylinder at 5 °C.

5) What is the volume of 45 grams of Argon gas at a pressure of 85.6 kPa and 26.0 °C?

• Atmospheric pressure is measured using a______.

• The pressure of a gas is measured using a ______. o A Manometer is a device to measure the pressure of an enclosed gas sample. A common simple manometer consists of a U shaped tube of glass filled with some liquid. Typically the liquid is mercury because of its high density. o The height difference determines the pressure.

Calculate the pressure inside each flask, given an atmospheric pressure of 760 mmHg.

Flask 200 mmHg Flask 350 mmHg

The gas in the flask has a higher pressure than The gas in the flask has a lower pressure than 760 mmHg. The pressure is . 760 mmHg. The pressure is .

Kinetic Molecular Theory Worksheet

1. The word kinetic comes from a Greek word that means “to move.” The kinetic molecular theory is based upon the assumption that particles of matter (atoms or molecules) are in constant

2. Of the three states of matter, which one has the most kinetic energy? 3. Which state of matter has particles that are separated by the largest distance?

4. A scientific theory is an explanation of some type of natural phenomena. Theories are normally developed from careful study of the way the world behaves. Let’s look at how gases behave and see if the kinetic molecular theory makes sense. 5. Compared to liquids and solids, gases tend to have ______densities. This can be explained because the particles of gas are ______. 6. If you apply pressure to a sample of gas, it is fairly easy to ______its volume (think about what would happen to a balloon if you squeeze it gently). This can be explained because there is a lot of ______between gas particles. 7. If someone sprays perfume in one corner of the room, eventually a person on the other side of the room can smell it. This can be explained because gas particles move and . In general, we would expect lighter gas particles to travel than heavier gas particles. 8. When two gases mix together or move through each other, this process is known as . When gas particles escape out of a tiny hole in a container, this process is known as ______. You should know the difference between these two words so you can avoid any confusion! 9. Kinetic molecular theory can be summarized as follows:

a. Gas particles are in constant . b. Gas particles are separated by relatively ______distances. c. When gas particles collide, they kinetic energy. d. Gas particles have attractive or repulsive forces between them. e. The kinetic energy of a gas is dependent on the of the gas.

Unit 6 Review: The Mole A. For the following questions, decide whether the following substances would be classified as an atom, molecule, or formula unit.

1. H2O ______

2. NaCl ______

3. Mg(NO3)2 ______

4. Ca ______

B. Given the following molecular formulas, what are the corresponding empirical formulas

1. Sodium Peroxide Na2O2 ______

2. Acetylene C2H2 ______

3. Terephthalic Acid C8H6O4 ______

4. Dinitrogen Tetroxide N2O4 ______

C. Solve the following problems.

1. Calculate the percent of phosphorus in barium phosphate. How many grams of phosphorus can be found in 63 g of Barium phosphate?

2. Cobalt is a metal that is added to steel to improve its resistance to corrosion. Calculate both the number of moles and the mass of a sample of cobalt containing 5.00 x 10 20 atoms.

3. Isopentyl acetate (C7H14O2), the compound responsible for the scent of bananas, can be produced commercially. Interestingly, bees release about 1 µg of this compound when they sting, in order to attract other bees to join the attack. How many molecules of isopentyl acetate are released in a typical bee sting? How many carbon atoms are present?

4. Carvone is a substance that occurs in two forms having different arrangements of the atoms, but the same molecular formula. One type of carvone gives caraway seeds their characteristic smell, and the other type is responsible for the smell of spearmint oil. Analysis of carvone gave the following percentages: C – 79.967%; H – 9.939% ; O – 10.650%. Determine the empirical formula for carvone.

5. Dichloroethane is a compound used as an additive to gasoline to help prevent knocking in engines. Analysis of this compound found that it contains 71.65% Cl; 24.27% C; and 4.07% H. Its molecular mass was found to be 98.96 g/mol. Determine both the empirical and molecular formulas for dichloroethane.

. 6. What is the percent by mass of water in CuSO4 5 H2O?

Gas Laws

1. If temperature is constant, the relationship between pressure and volume is a. Direct b. inverse 2. If pressure is constant, the relationship between temperature and volume is a. Direct b. Inverse 3. One way to increase pressure on a gas is to a. decrease temperature c. increase the number of gas particles b. increase volume d. lower the kinetic energy of the gas molecules 4. How do gas particles respond to an increase in volume? a. increase in kinetic energy and decrease in temperature b. decrease in kinetic energy and decrease in pressure c. increase in temperature and increase in pressure d. increase in kinetic energy and increase in temperature 5. If pressure of a gas is increased and its volume remains constant, what will happen to its temperature? a. Increase c. stay the same b. decrease 6. If a gases volume is decreased and pressure is constant, its temperature will a. Increase c. remain the same b. decrease 7. If the temperature of a gas remains constant but pressure is decreased, the volume will a. Increase c. remain the same b. decrease 8. Convert 2.3 atm into mmHg. a. 2300 mmHg c. 2.3 mmHg b. 1750 mmHg d. 0.0030 mmHg 9. Convert 6.7 liters into milliliters. a. 0.0067 mL c. 5092 mL b. 0.0088 mL d. 6700 mL 10. The pressure of a gas is 750.0 torr when its volume is 400.0 mL. Calculate the pressure (in atm) if the gas is allowed to expand to 600.0 mL at constant temperature. a. 0.660 atm c. 500.0 atm b. 1.48 atm d. 1125 atm 11. The volume of a gas is increased from 150.0 mL to 350.0 mL by heating it. If the original temperature of the gas was 25.0 °C, what will its final temperature be (in °C)? a. 146°C c. 58.3°C e. 695°C b. 10.7°C d. 422°C 12. A gas exerts a pressure of one atm at standard temperature (273.0 K). What must the temperature be adjusted to for the gas to exert a pressure of 4.00 atm? (Give your answer in °C) a. -205°C c. 819°C b. 68.3°C d. 1092°C 13. A quantity of gas has a volume of 250.0 liters at 17.0°C and 3.00 atm of pressure. To what volume must the gas be increased for the gas to be under STP conditions? a. 78.4 L d. 771 L b. 88.5 L e. 797 L c. 706 L 14. What are standard temperature and pressure conditions for gases? a. 0°C and 0 torr c. -273°C and 1 atm e. 0°C and 1 torr b. 0 K and 760 torr d. 0°C and 760 torr 15. If the volume of a confined gas is doubled while the temperature remains constant, what change (if any) would be observed in the pressure? 29

a. It would be half as large. d. It would be 1/4 as large. b. It would double. e. It would remain the same. c. It would be four times as large. 16. A given mass of gas in a rigid container is heated from 100°C to 500°C. Which of the following responses best describes what will happen to the pressure of the gas? a. The pressure will decrease by a factor of five. b. The pressure will increase by a factor of five. c. The pressure will increase by a factor of about two. d. The pressure will increase by a factor of about eight. e. The pressure will increase by a factor of about twenty-five. 17. Which of the following has the most molecules? a. 1.00 L of CH4 at 0°C and 1.00 atm d. 1.00 L of CO2 at 50°C and 1.25 atm b. 1.00 L of N2 at 0°C and 1.00 atm e. 1.00 L of CO at 0°C and 1.25 atm c. 1.00 L of O2 at 20°C and 1.00 atm 18. Avogadro stated that equal volumes of gases under the same conditions of temperature and pressure have equal a. numbers of molecules. d. atoms. b. numbers of grams. E. speeds c. molar masses. 19. What volume of CH4 at 0°C and 1.00 atm contains the same number of molecules as 0.50 L of N2 measured at 27°C and 1.50 atm? a. 0.37 L d. 0.50 L b. 0.46 L e. 0.82 L c. 0.68 L 20. If 3.0 L of helium at 20.0°C is allowed to expand to 4.4 L, with the pressure remaining the same, what is the new temperature? a. 702°C d. 30.0°C b. 430°C e. 55°C c. 157°C 21. At what temperature will 41.6 grams N2 exerts a pressure of 815 torr in a 20.0 L cylinder? a. 134 K d. 337 K b. 176 K e. 400 K c. 238 K 22. A mixture of the gases neon and krypton is in a 2.00 liter container. The partial pressure of the neon is 0.40 atm and the partial pressure of the krypton is 1.20 atm. What is the mole fraction of neon? a. 0.20 d. 0.60 b. 0.25 e. 0.80 c. 0.33 d. e. 23. Which of the following gases has the greatest density at 0°C and 1 atm? a. N2 d. Ne b. 02 e. CO c. F2

24. What volume of O2, collected at 22.0°C and 728 mmHg would be produced by the decomposition of 8.15 g KClO3? 2KClO3(s)  2KCl(s) + 3 O2(g) 30

a. 1.12 L d. 2.23 L b. 1.48 L e. 2.52 L c. 1.68 L

25. Ammonia gas is synthesized according to the balanced equation N2(g) + 3H2(g)  2NH3(g) If 15.0 liters of nitrogen are reacted with an excess of hydrogen, how many liters of ammonia could be produced? Assume all gas volumes are measured at the same temperature and pressure. a. 5.00 L b. 10.0 L c. 15.0 L d. 20.0 L e. 30.0 L

26. A gas has a volume of 3.4 L at 25 °C, what is the final temperature if the volume increases to 4.7 L?

27. The initial pressure of a gas is 457 mm Hg, the final volume is 750 mL with a final pressure of 650 mm Hg. What is the initial volume of the gas?

28. A gas of 3.4 moles occupies a volume of 40.6 mL at 298 K, what is the pressure of the gas?

29. A gas of 1 mole has a temperature and volume at STP, the temperature of the gas is increased to 311 K.

30. At 18 °C , 34.7 grams of carbon dioxide gas creates a pressure of 613 mm Hg, what is the volume of the gas? Hint: get into the correct units before you start.

31. A 3.00 L pocket of air at sea level has a pressure of 100 atm. Suppose the air pockets rise in the atmosphere to a certain height and expands to a volume of 10.0 L. What is the pressure of the air at the new volume?

32. The gas in a balloon occupies 3.50 L at 300. K. At which temperature will the balloon expand to 8.50 L?

33. A gas is collected by water; it contains 78.5 atm of nitrogen, 998.7 atm of oxygen and 324.1 atm of hydrogen. Determine the total pressure of this gas.

34. A weather balloon has a volume of 1750 L at 103 kPa. The balloon is released to the atmosphere. At the highest point above the ground, the pressure on the balloon is 35.0 kPa. What is the new volume of the balloon at this height?