Gas Laws Packet Page 1 of 23
CP Chemistry Unit 9: Gases, Gas laws & Gas Stoichiometry – Ch. 12
Quiz: Wednesday, May 14
Test: Friday, May 16
PS Due : Friday, May 16
VOCABULARY:
Ideal gas
standard atmospheric pressure
Diffusion
effusion
CONSTANTS/FORMULAS:
Boyle’s law (P1 V1 = P2 V2)
Combined gas law
Ideal gas law
standard temperature
molar volume
Charles’ law (V1/T1 = V2/T2)
Dalton’s law
Molar volume
STP
Gay-Lussac’s law (P1/T1 = P2/T2)
Graham’s law
Molecular mass Determination (of a gas)
Avogadro’s law
OBJECTIVES:
 Memorize the values for STP.
 Memorize and be able to apply the gas laws: Boyle’s, Charles, Dalton’s law of partial pressure, combined gas law, Gay-Lussac’s,
and Graham’s. (some laws in the packet) You do not need to know the names.
 Be able to use molar volume of a gas at STP in problems.
 Memorize and be able to apply the ideal gas law.
 Use the gas constant R = .0821 L-atm/mol-K.
 Be able to do problems involving gas stoichiometry (at STP and other conditions)
Unit 9 EQs
Day 1 Review
 Given 2 MgO + 2 S  2 MgS + O2
a. If 5.0 g of S reacts with excess MgO – what mass of MgS can be produced?
b. If 5.0 g of S reacts with excess MgO at STP – what volume of oxygen gas can be produced?
 Given Cl write
a. the long form electron configuration
b. the noble gas configuration
c. the dot diagram
d. list 2 other elements with similar chemical properties (to Cl)
e. list 2 other elements with similar atomic radii
f. list 2 other elements with similar electronegativities
Day 2 New Material
 The volume of a gas is 400.0 ml at 1.1 atm. What would the volume be at 1.8 atms?
 If the pressure of 2.1 L of a gas at 30 0C is 1.3 atm, what would the pressure be of 1.8 L of the same gas at 35 0C
 Which gas would move the slowest at STP: hydrogen, oxygen or carbon monoxide?
Day 3
 Using the ideal gas law, What pressure is exerted by 1.2 mol of a gas with a temperature of 20.0 0C and a volume of 9.2 L?
 What is the mass of 1.5 L of Helium gas at a pressure of 685 mm Hg and 30 0C? (hint- find moles first then convert!)
Day 4
 Given Fe + O2 FeO2
a. How many grams of iron (IV) oxide can be produced from 15.0 L of oxygen gas at STP?
b. Using the same equation how many grams of iron (IV) oxide can be produced from 15.0 L of oxygen gas at 400 K and
2.2 atm?
Gas Laws Packet Page 2 of 23
Stoichiometry Road Map
How To Use The "Roadmap" For Solving Chemistry Problems
* 1. Write all the compounds and elements in the problem correctly.
* 2. Write the balanced chemical equation for the problem.
* 3. Write the MATERIAL you have enough information about to use as GIVEN. (This has been one of the major stumbling blocks in
using the roadmap.) If you know the number of moles, the mass, or the number of molecules of a material, you have all you need to
start the problem. You need CONCENTRATION AND VOLUME of a solution to have the amount of solute that reacts. You need
VOLUME AND DENSITY of a solid or liquid to have an amount of that. You need VOLUME, PRESSURE AND TEMPERATURE
of a gas to have a complete set of information. (Notice it is useful to understand the properties of the states of matter as you do this.)
* 4. Write what you need to FIND and all the other pertinent information about that material. For instance, if you need to find the
volume of a gas, you must also list the pressure and temperature of that gas in FIND. In this manner: FIND V, volume of gas at 79 0C
and 1.8 atm.
* 5. Sketch out an outline of the math according to the roadmap. You know there are some points in the roadmap that you miss on the
outline because they are calculated in the process, for instance if you are given a mass of one material and asked to find the density of
another material with its volume, you would start at the MASS GIVEN and use the FORMULA WEIGHT to get to the MOLES
GIVEN, but MOLES GIVEN does not appear in the outline because it is already calculated. You next need the MOLE RATIO to get
the MOLES FIND. Again, MOLES FIND does not appear in the outline.
* 6. Fill in the outline with the numbers, units and materials (for instance, 15 kg Mg) and do the calculations. Be careful of numbers
that need to be inverted. You can tell the coefficients that need to be inverted by the units.
Gas Laws Packet Page 3 of 23
Unit 10 - Gas Laws Notes
Gas Laws Notes
Gases: 4 measureable quantities:
Volume
Temperature
Pressure
Number of moles
Variable
Unit(s)
We will assume the gases are ideal gases: gases that follow model behavior; gases are most likely to act ideally when the pressure is
low and the temp is high (this is when gases can move freely without being attracted to each other).
STP?
Gas Pressure conversions: in packet- 1 atm = 101.3 kPa = 760 mm Hg = 760 torr (all equivalent) Pressure = force over area
Example: Convert 720 torr to kPa
You try: Convert 1.8 atm to mm Hg
GAS LAWS – Must be Memorized You Do NOT have to know the name.
Boyle’s law
inversely?
V varies inversely with P
P 1 V1 = P 2 V2
Graph of P vs V:
EX. If 1.0 L of a gas at 1.2 atm is allowed to expand to 5.0 L, what is the new pressure?
You try: A sample of O2 gas has a volume of 150 ml when its pressure is 720 mm Hg, what will the volume be if the pressure is
increased to 750 mm Hg?
(Answer: 144mL)
Charles law: V varies directly with the Kelvin temperature V 1/T1 = V2/T2
T must be in Kelvin Directly?
Graph of V vs T:
Ex: A helium filled balloon has a volume of 2.75 L at 20.0 0C . The volume of the balloon decreases to 2.46 L after it was placed
outside on a cold day. What is the outside temperature?
Gas Laws Packet Page 4 of 23
You try: A sample of neon occupies a volume of 752 ml at 25 0 C. What volume will the gas occupy at 50. 0C?
(Answer: 815 mL)
Gay-Lussac’s Law: P varies directly with Kelvin Temperature P 1/T1 = P2/T2
Like which other law?
Example: Before a trip from Greensboro to NY, the pressure in a tire is 1.8 atm at 20 0C. At the end of the trip the pressure gauge
reads 1444 mm Hg. What is the new temperature in the tire?
(Answer: 309 K or 36° C)
You try: If the pressure of a gas at 25 0C is 3.2 atm – what would the pressure be at 55 0C?
Combined gas law: P1V1 = P2V2
T1
T2
T in K!!!
Ex: a 700. ml gas sample at STP is compressed to a volume of 200. ml, and the temperature is increased to 30.0 0C. What is the new
pressure of the gas ?
(Answer: 394 kPa)
You try: If 282.4 ml of a gas at 25 0C and 1.3 atm is cooled to 20. 0C and 780 mm Hg. What is the new volume?
Avogadro’s law Volume and moles are directly related
V1 = V2
n1
n2
You try: 5.00 L of a gas is known to contain 0.965 mol. If the amount of gas is increased to1.80 mol, what new volume will result?
Gas Laws Packet Page 5 of 23
Dalton’s law of Partial Pressure: pressure of each gas in a mixture is called the partial pressure of that gas.
Total Pressure = sum of partial pressures
PT = P1 + P2 + P3 etc
Example: A 10.0L container of nitrogen and helium gases has a total pressure of 3.2 atm, if the helium’s partial pressure is 1.1 atm –
what is the partial pressure of the nitrogen gas?
You try: The total pressure inside a balloon containing helium, hydrogen and oxygen is 12.2 atm – if helium’s partial pressure is 1.0
atm and hydrogen’s partial pressure is 3.0 atm– what is the partial pressure of the oxygen?
Special case: gases collected by water displacement
Use formula
PT =
Patm
= Pg + PH2O
Total atmosphere
gas
water
Patm from lab/given
(Vapor pressure of water: Table p. 483 Prentice Hall Book)
Ex: Oxygen is collected by water displacement. The barometric pressure and temperature are 84.5 kPa and 20.0 0C. What is the
partial pressure of O2?
You try: A gas is collected over water and the atmospheric pressure is 101.1 kPa at 50 C. What is the partial pressure of the gas?
(Answer: 88.8 kPa)
Graham’s Law
Effusion?
Diffusion?
Rate of effusion and diffusion varies inversely with the mass of the gas. The lighter a gas the faster it moves (the heavier a gas
the slower it moves).
Rate of gas A = Square Root Mass of gas B
Rate of gas B
Mass of gas A
Ex: Which gas would diffuse the fastest at STP: Hydrogen, neon or oxygen?
You try: Compare the rates of effusion of fluorine and chlorine.
(Answer: fluorine is 1.4 x faster than chlorine)
Gas Laws Packet Page 6 of 23
GAS LAW PROBLEMS:
Work the following problems and identify the gas law used; be sure your answer includes units!
1. A gas occupies a volume of 35.9 ml at a temperature of 22.0 C. What volume will the same gas occupy at a temperature of 28.0
C?
2.
At a pressure of 780 mm Hg and 24.2 C a gas has a volume of 350.0 ml. What will the volume of this gas be under standard
conditions (1 atm and 273 K)?
3.
A gas occupies a volume of 24.8 ml at 725 torr. What will the pressure of the gas be at 22.5 ml?
4.
At 25 0C the pressure of a gas is 1.7 atm. At what temperature will the pressure be 2.3 atm?
5.
If 45.0 ml of a gas is under 1.3 atm of pressure; at what pressure will the volume be 60.0 ml?
6.
Which moves the fastest: nitrogen or bromine gas (at the same temperature and pressure)?
7.
A gas at a temperature of 67.5 C and a pressure of 882 torr occupies a volume of 242.2 ml. What will the volume of the gas be at
840 torr and 80.0 C?
8.
A mixture of gases has a pressure of 12.2 atm; if the first gas has a pressure of 2.2 atm and the second gas has a pressure of 3.2
atm – what is the pressure of the remaining gas?
9.
A gas is collected over water and the atmospheric pressure is 95.5 kPa at 30 0C. what is the partial pressure of the gas?
10. If 2.1 mol of a gas has a volume of 1.5 L; what will the volume of 2.7 mol of the same gas under the same conditions be?
Gas Laws Packet Page 7 of 23
Ideal Gas Law notes
PV = nRT
Must use the following units with the ideal gas law!
P = atm V = L T = K
n = moles
R = gas constant 0.0821 L-atm/mol- K (in packet!)
Example: What is the pressure exerted by a 12.0 g sample of Nitrogen gas (N 2) in a 10.0 L container at 25 0C?
You try: What is the volume of 15.0 mol of a gas at a pressure of 120 kPa and a temperature of 55 0C?
Practice on ideal gas law worksheet!
Gas Stoichiometry Notes Most of this is review!
Molar Volume 1 mol of any gas at STP has a volume of 22.4 L
1 mol = conversion factor (only to be used at STP)
22.4 L
Ex. What is the mass of 98.0 ml of sulfur dioxide at STP? (work together on board – copy)
Stoichiometry of Gases (this is review!)
Ex. Given: C3H8 (g) + 5 O2 (g)  3 CO2 (g) + 4 H2O (l)
How many L of O2 are required to react with 0.35 g of propane at STP?
Ex 2 Given: C3H8 (g) + 5 O2 (g)  3 CO2 (g) + 4 H2O (l)
How many L of O2 are required to react with 0.35 g of propane at 85 0C and 1.8 atm?
You try:
How many L of CO at 27 0C and 788 mm Hg can be produced from 65.5 g of carbon?
2 C (s) + O2 (g)  2 CO (g)
Gas Density: D = ?
At STP : D = Molar mass
Molar volume
g/mol (PT)
22.4 L/mol
Ex: What is the density of CO2 at STP?
You try: What is the molar mass of a gas with a density of 1.56 g/L ?
Gas Laws Packet Page 8 of 23
Molecular Mass Determination from Ideal Gas Law:
(see derivation on board)
D = PM
RT
density = pressure (atm) x molar mass (PT)/ constant x temp (K)
Examples & practice on ideal gas law worksheet!
Stoichiometry of Gases
Can do L-L conversions (just like mol-mol) with 2 gases and an equation
Example: Given: C3H8 (g) + 5 O2 (g)  3 CO2 (g) + 4 H2O (l)
How many L of O2 are required to react with 0.35 L of propane?
**You may have to use molar volume!**
**You may have to use the ideal gas law!**
Example 2: Given CaCO3 (s)  CaO (s) + CO2 (g)
How many grams of calcium carbonate must decompose to from 5.0 L of CO 2 at STP?
You try: If 10.0 g of lithium chloride decomposes how many liters of Cl2 gas are produced at STP? (write a balanced equation first!)
Example 3: How many liters of H2 at 35 oC and 745 mm Hg are need to react completely with 825 g of WO 3?
WO3(s) + 3H2 (g)  W(s) + 3H2O (l)
You try:
How many L of CO at 27 0C and 788 mm Hg can be produced from 65.5 g of carbon?
2C(s) + O2(g)  2CO(g)
Gas Laws Packet Page 9 of 23
Worksheet Ideal Gas Law
Remember: PV = nRT and D = PM/RT
Must use atm, L, moles and K R = .0821 L-atm/mol-K
1. How many moles of oxygen will occupy a volume of 2.5 liters at 1.2 atm and 25 0C ?
2. What volume will 2.0 moles of nitrogen occupy at 720 torr and 20.0 0C?
3. What pressure will be exerted by 25 g of CO2 at a temperature of 25 0C and a volume of 500. ml?
4. At what temperature will 5.00 g of Cl2 exert a pressure of 900. torr at a olume of 750. ml?
5. How many moles of nitrogen gas will occupy a volume of 347 ml at 6680 torr and 27 0C?
6. Find the number of grams of CO2 that exerts a pressure of 785 torrs at a volume 32.5 L and a temperature of 32 0C.
7. How many moles of nitrogen gas will occupy a volume of 347 ml at 6680 torr and 27 0C?
8. What volume will 454 grams of hydrogen occupy at 1.05 atm and 25 0C? (remember hydrogen is diatomic!)
9. Find the number of grams of CO2 that exerts a pressure of 785 torrs at a volume 32.5 L and a temperature of 32 0C.
10. An elemental gas has a mass of 10.3 g. If the volume is 58.4 L and the pressure is 758 torrs at a temperature of 2.5 0C, what is the
gas (Hint find the molar mass!)
Gas Laws Packet Page 10 of 23
WORKSHEET GAS STOICHIOMETRY and IDEAL GAS LAW
1.
What is the density of nitrogen trioxide at STP?
2.
How many moles of helium gas are there in 23 L of helium at STP?
3.
What is the volume of 1.5 g of PCl gas at 545 mm Hg and 55 C?
4.
How many moles of iodine gas are there in 550 ml of gas at 2.1 atm and 27 C?
5.
At STP how many liters of carbon monoxide can be produced from burning 32.5 g of oxygen according to the following equation:
2 C (s) +
O2 (g) 
2 CO (g)
6.
Using the above equation, what volume of oxygen is required to produce 375 ml of CO at STP?
7. What volume of oxygen in liters can be collected at 750 mm Hg and 25.0 C when 36.0 g of KClO 3 decomposes according to the
following equation? BALANCE THE EQ FIRST! KClO 3  KCl + O2
8. What is the mass of 1258 ml of hydrogen gas at STP?
Gas Laws Packet Page 11 of 23
Gas Review worksheet covering whole unit!
1.
A cylinder of argon gas contains 50.0 L of Ar at 18.4 atm and 127 °C. How many moles of argon are in the cylinder?
2.
A gas sample is at 27 °C. If the temperature is raised to 77 °C and the initial pressure was 1500 mmHg, what is the final pressure?
3.
A sample of helium was compressed from a volume of 0.5 L to 0.25 L where the pressure is 500 mmHg. What was the original
pressure?
4.
A hot air balloonist puts 125,000 Liters of air into their balloon at 27 0C. When they heat the air to 200 °C at constant pressure,
what is the final volume of the air in the balloon?
5. When measured at STP, a quantity of gas has a volume of 500 L. What volume will it occupy at 0°C and 93.3 kPa?
6. A mixture of gases contains helium with a pressure of 2.5 atm and carbon dioxide with a pressure of 4.5 atm – what is the total
pressure of the container?
7. For the reaction 2 H2(g) + O2(g)  2 H2O(g), how many liters of water can be made from 5 L of oxygen gas and excess hydrogen gas
at STP?
Gas Laws Packet Page 12 of 23
8. A 3.10 mL bubble of methane gas forms at the bottom of a bog where the temperature is 12 oC and the pressure is 8.5 atm. The
bubble rises to the surface where the temperature is 35 oC and the pressure is 1.18 atm. What is the new volume of the methane
bubble?
9. How many liters of oxygen gas can be produced by the decomposition of 10.0 g of water at STP?
2 H2O  2H2 + O2
10. What is the volume of 12.5 moles of argon gas with a pressure of 3.3 atm at 25 0C.
11. Which gas moves the fastest: Nitrogen, chlorine, neon, hydrogen or helium?
12. A gas is collected over water and the atmospheric pressure is 98.1 kPa at 40 0C. what is the partial pressure of the gas?
Gas Laws Packet Page 13 of 23
STOICHIOMETRY WORKSHEET
Work the following stoichiometry problems in the space provided.
1. Write the correctly balanced equation for the decomposition of MgCl 2.
2. Using the above equation and given 5.0 grams of MgCl2, how many grams of magnesium are produced?
HINT: grams  moles  mole ratio  moles  grams
3.
What is the volume of 1 mole of a gas at STP?
4.
Using the equation from #1 determine the volume of chlorine gas produced from 5.0 grams of magnesium chloride.
5.
Balance the following equation:
 Cu +  HNO3   Cu(NO3)2 +  H2
6.
Given 2.00 grams of copper and an excess of nitric acid how much hydrogen gas is produced?
7.
How many grams of copper (II) nitrate are produced?
Answer the following questions about the ideal gas law.
8.
Write out the ideal gas equation?
9.
What is the ideal gas constant?
10. What is the volume of a gas at a pressure of 1.2 atm, a temperature of 301 K and 2.00 moles.
Gas Laws Packet Page 14 of 23
Practice sheet #2 gas unit
Show all work – include units on the answer
1.
Convert the following pressure units: A. 1.3 atm to kPa: _______________
B. 795 mm Hg to atm: _______________
2.
Sketch the graph of the following pairs of variables:
P
P
V
V
T
T
3. 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?
____________
4. On hot days, you may have noticed that potato chip bags seem to “inflate”, even though they have not been opened. If I have a 250
mL bag at a temperature of 19°C, and I leave it in my car which has a temperature of 60°C, what will the new volume of the bag be?
____________
5. If I have an unknown quantity of gas at a pressure of 1.2 atm, a volume of 31 L, and a temperature of 87°C, how many moles of gas
do I have?
____________
6. If I have 66 g of oxygen gas at a temperature of 67°C, and a volume of 8.89 L, what is the pressure of the gas?
___________
7. At STP how many liters are in 25 g of carbon dioxide gas?
______________
Gas Laws Packet Page 15 of 23
8. How hot will a 2.3 L balloon have to get to expand to a volume of 4.0 L? Assume that the initial temperature of the balloon is
25°C.
__________________
9 Write an equation for the formation of water from hydrogen and oxygen gas.
__________________
10 Using the above equation how many g of water can be produced from 10.0L of hydrogen gas at STP?
___________________
11 Using the above equation how many g of water can be produced from 10.0 L of hydrogen gas at 75 0C and 0.78 atm of pressure?
__________________
12 If I have 4 moles of a gas at a pressure of 5.6 atm and a volume of 12 L, what is the temperature?
_____________________
13 Which gas will move fastest: Argon, Chlorine or Krypton?
____________________
Gas Laws Packet Page 16 of 23
GASES TEST REVIEW
INFORMATION TO BE MEMORIZED:
As practice; write the formulas without your notes! You may use your packet
Charles’ Law
Boyle’s Law
Gay-Lussac’s Law
Combined gas law
Dalton’s law
Graham’s law
Ideal gas law
R=
Molar volume at STP
STP =
PRACTICE PROBLEMS: Work without your notes!
1. If 259 ml of oxygen gas is at 112 kPa, what will the volume be at standard pressure?
2. A vessel with a pressure of 12.0 atm contains a mixture of helium and oxygen; if the helium exerts a pressure of 2.0 atm what is the
partial pressure of oxygen?
3. What is the volume of a gas at 273 K, if it had a volume of 22.8 ml at 48 C?
4. If a 25 ml of sulfur dioxide is at 37 C and 90.2 kPa, what will the temperature be if the volume becomes 19.6 ml and the pressure is
760 torr.
5. What is the volume of 156 grams of chlorine gas at STP?
6. What is the pressure exerted by 1.32 moles of gas in an 18 L vessel at 27 C?
7. A 759 ml vessel contains 0.0945 mol of a gas at 98.6 kPa. What is the temperature of the gas?
8. What volume of hydrogen gas at STP will be produced from 16.7 g of magnesium reacting with an excess amount of hydrochloric
acid?
9. Which one of the following will diffuse the fastest at STP: NH3, CH4, Ar, HBr?
ANSWERS:
1. 286 ml
5. 49.2 L
9. CH4
2. 10 atm
6. 1.81 atm
3. 19.4 ml
7. 95.3 K
4. O C (273 K)
8. 15.3 L H2
Gas Laws Packet Page 17 of 23
Air Bag Lab
This lesson is about how air bags work. However, it is also a lesson about chemical reactions and the use of measurements and
documentation.
When the Mars rover landed on Mars, it was surrounded by air bags as it hit the surface. It used the same technology and science as
the air bag in your car.
Background Information:
The automobile air bag is a remarkable device. It is deceptively simple in concept, but the design requirements of the system are
actually very demanding. When a crash occurs, an air bag must inflate rapidly (within about 40 milliseconds), cushioning the
occupants against impact. The gas produced must be non-toxic, odorless, and cool enough to avoid burning the occupants. You’d also
like the compounds used to be stable, and non-toxic, so they don’t expand unexpectedly and are easy and safe to dispose of.
Sensors detect impact and electrically initiate the following reduction-oxidation reaction to activate modern air bags:
2 NaN3(s) → 2Na(s) + 3N2(g)
Sodium azide (NaN3) is a stable solid and a small pellet that can easily be stored in air bag compartments. The huge volume of
nitrogen (N2) gas is produced rapidly and is non-toxic and relatively cool. Sodium azide itself, however, is pretty nasty. A few
micrograms per liter are often used to prevent bacterial growth in biological preparations. Toxic chemicals like sodium azide are a
major concern in landfills where undeployed air bags are discarded.
The sodium metal produced also has some exciting chemistry. It reacts violently (explosively) with water (and hence your skin).
Fortunately, sodium metal can be transformed using a reduction-oxidation reaction into the relatively inert compound NaFeO2 by
adding Fe2O3 (iron oxide or rust) to the pellet. The pellets also contain additives that enhance the rate at which the gas is produced
while minimizing the heat. Some formulations are trade secrets, but all require a careful chemical, environmental and economic
analysis. These issues, as well as the quest for better and cheaper systems, keep open the search for other compounds and formulations
for the gas-producing reaction used in the system.
Objective: Assemble the perfect amount of reactants needed to completely fill, but not burst, an airbag.
Safety: This lab involves the use of Hydrochloric Acid. Hazards are chemical burns and irritation to lung tissue. Do Not breath in
fumes. If spilled on skin wash with soap and water. Goggles at all times!
Materials:
 1 Zip Lock Bag
 Baking Soda (Sodium Bicarbonate – NaHCO3)
 1.0 M Hydrochloric Acid (HCl)
 1 Spatula
 1 small plastic dish
 100 ml graduated cylinder
Steps:
1.
Determine the volume of your Ziploc bag in Liters.
Answer :________ Liters
2.
3.
How many Liters of CO2 gas will your Ziploc bag hold?
Answer : ________ Liters
In the box below, write the correct chemical equation for the following reaction:
Hydrochloric acid + Sodium Bicarbonate -- Carbon Dioxide + Sodium Chloride + Water
4.
Balance the equation in the above box.
Gas Laws Packet Page 18 of 23
5.
Calculate how many moles of CO2 your Ziploc bag will hold.
Answer : ________ Mol CO2
6.
Calculate how many moles of Sodium Bicarbonate are needed to produce your answer to question #5.
7.
Convert your answer to question # 6 to grams of Sodium Bicarbonate.
Answer : _________ Mol
Answer: __________ g
8.
9.
Calculate how many moles of Hydrochloric acid are needed to produce your answer to question #5
Answer : _________ Mol
Use the “Molarity” equation to determine how many milliliters of Hydrochloric acid are needed.
Molarity = moles
Liters
Answer: __________ mL
Time to test your results
10. Carefully measure out an exact amount of Sodium Bicarbonate from Question # 7 into the small plastic dish. Slide the dish
into your Ziploc bag without spilling the Sodium Bicarbonate.
11. Carefully measure out an exact amount of Hydrochloric Acid from Question #9 into a graduated cylinder. Carefully poor the
Hydrochloric acid into the Ziploc bag WITHOUT getting the Sodium Bicarbonate wet.
12. Carefully seal the Ziploc bag shut. Be sure it is completely sealed.
13. Carefully bring your Ziploc bag AND this sheet to me at the front lab without letting the reactants mix. When you get to the
front we will mix it and see if you created a useable air bag.
MRS REID’S INITIALS:___________
Gas Laws Packet Page 19 of 23
Flick your Bic – Molar Mass Determination of Butane lab
Objective: To use the ideal gas law to determine the molar mass of butane.
Equipment: As part of your pre-lab make an equipment list after reading the procedure
Procedure:
1. Get a lighter out of the water filled beaker in the front. Dry the lighter off and weigh your lighter.
2. Fill a graduated cylinder up with water and invert it into a large beaker/container.
3. Through water displacement collect about 50 ml of butane gas in your cylinder. You will do this by placing the lighter under the
water into the mouth of the cylinder. Then press the button to release gas into the cylinder – the gas should displace the water and
you should get a graduated cylinder filled with gas – do not lit the lighter.
4. Cork your cylinder with a stopper and release the butane out the window – do not inhale.
5. Dry off your lighter and reweigh it. Return it to the beaker at the front.
6. Use a thermometer to get the temperature of the room:
7. Check the board to get the atmospheric pressure
Data Table: (include units!)
Mass of Butane lighter (before): _______________
Mass of Butane lighter (after): _____________
Mass of butane used: _______________
Volume of water displaced =volume of butane used: ________________
Temperature of the room: _________________
Atmospheric pressure: ___________________
---------------(The rest of the table is filled in AFTER doing the lab questions!)-----------------------Pressure of the butane: __________________
Moles of butane: ____________________
Molar mass of butane: __________________
Percent error: _________________
Calculations: Show all work! Be sure to copy your final answers onto the data table above.
1. Using Dalton’s law of partial pressure – calculate the partial pressure of the butane.(table – pg 899)
2. Using the ideal gas law calculate the moles of butane
3.
Using your answer to number two and your mass of butane use – calculate the molar mass of butane. (divide your mass of
butane by your moles from # 2)
4.
5.
Gas Laws Packet Page 20 of 23
The percentage composition of the gas in the lighter is as follows: carbon, 82.63% and hydrogen, 17.37%. Calculate the
empirical formula for butane. (remember H is not diatomic in compounds!)
Using your molar mass, see if you can get a whole-number multiple of the empirical formula for the molecular formula of
the gas. (Using the empirical formula from # 4 and your molar mass from number 3 try to find a whole number ratio and
write the molecular formula for butane – if you need help check out your notes on emp/molecular formulas in the mole unit!)
Write the molecular formula you found for butane here:________
6.
Given that the molar mass of butane is 58 g/mol – calculate your percent error.
Questions:
1. How do you explain the fact that the gas is a liquid in the lighter, but a gas when it is collected?
Make an Error analysis table – listing at least two possible errors and their effect on molar mass (would it be higher or lower – and
why
1.
2.
Conclusion: In this lab I used several gas laws. Including the ideal gas law; in the ideal gas law
R is called _____________________ and its value with units is _________________.
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Unit 9 – Gas Laws Problem set:
Review:
1. Draw the Lewis Structure for the following and identify the VSEPR Shape and identify if they are polar or nonpolar:
a. carbonate
b. silicon disulfide
Show your work for the following questions. Credit will not be given without work. Include units on your answers.
2. Given Fe2O3 + 2 Al  2 Fe + Al2O3
a.
What is the name of Fe2O3 ?
______________
b.
If 9.0 g of Al reacts with excess Fe2O3 how many grams of aluminum oxide will be produced?
Final answer:
3.
___________________
What is the wavelength for a Hydrogen electron that jumps from n = 4 to n = 1.
Wavelength:_____________
What type of energy is this? _____________ (Do not use visible as an answer!)
4.
For the following pairs which would have the higher boiling point? Why ?
a.
HCl or H2O
higher boiling point:____________
Because:
b.
NaCl or C12H22O11 higher boiling point:____________
Because:
5.
Given the following compounds ID the bond type, if it is covalent ID the intermolecular force and then rank the compounds
from highest boiling point to lowest boiling point.
Compound
Platinum wire (Pt)
LiCl
H2O
MgO
O2
Bond type
Gas Laws Packet Page 22 of 23
b. List in order from highest boiling point to lowest boiling point: (please use symbols!)
________
__________
_________
__________
___________
6. A sample of diborane gas (B2H6) a substance that bursts into flame when exposed to air, has a pressure of 345 torr
at a temperature of –150C and a volume of 3.48 L. If conditions are changed so that the temperature is 360C and the
pressure is 268 torr, what will be the volume of the sample?
7. The density of a gas was measured at 1.30 atm and 470C and found to be 1.95 g/L. Calculate the molar mass of
the gas.
8. Mixtures of helium and oxygen are used in scuba diving tanks to help prevent “the bend”. For a particular dive,
46 L of O2 at 250C and 1.0 atm and 12 L He at 250C and 1.0 atm were pumped into a tank with a volume of 5.0 L.
Calculate the partial pressure of each gas and the total pressure in the tank at 25 0C. Hint: Label all of the variables
and calculate each tank (oxygen and helium) as separate problems!
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9. What is one every day application of one or more of the gas laws. Be specific and illustrate your example. (You
may draw, cut out a picture, download a graphic, etc.)
10. Calculate the volume of oxygen gas at STP, required for the complete combustion of 45 g of octane (C 8H18).
11. Calculate the volume of oxygen gas at 85 0C and 789 torr, required for the complete combustion of 45 g of octane
(C8H18).
(extra-credit): A sample of methane gas having a volume of 2.80 L at 25 0C and 1.65 atm was mixed with a sample
of oxygen gas having a volume of 35.0 L at 310C and 1.25 atm. The mixture was then ignited to form carbon dioxide
and water. Calculate the volume of CO2 formed at a pressure of 2.50 atm and a temperature of 1250 C.