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Honors Chemistry Name _________________________________ Period
___ Date ______/______/______
Unit 8 - Chapter 13 Notes - Gases U n i t 8 : G a s e s
Conversion Factors that you will use throughout this unit:
1 atmosphere = 101.3kPa = 760.0 mm Hg (torr) = 14.70 psi Gas
Constant: R = 0.08206 L. atm K-1 mol-1 = 8.314 L .kPa K-1 mol-1 0oC
= 273K Volume of one mole of gas: 22.4L at 0oC and 101.3kPa 24.45L
at 25oC and 101.3kPa List at least 5 other real life examples of
gases and their uses/effects. 1. 2. 3. 4. 5.
Demonstrations on Air Pressure: Balloon in a vacuum -
Observations: Explanation Hot water in a vacuum - Observations
Explanation (From this demonstration, does water on top of a
mountain boil at a higher or lower temperature?) Water in a can;
heated and inverted in cold water: Observations: Explanation
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Pressure (Zumdahl Ch. 13.1) What is pressure? P = F/A Where F=
force A = Area (example stepping on your foot with spike shoes or
flat shoes which exerts more pressure? Why?) Pressure of a gas
depends on: Symbol Units Temperature of the gas
Volume of the container
Number of molecules
Atmospheric pressure results from the mass of the air being
pulled toward the center of the earth by gravity. Varies with
altitude. A device that measures the atmospheric pressure is the
barometer.
What happens when the air pressure is high?
Air pressure is one of the most important factors that determine
what the weather will be like.
http://www.kentchemistry.com/images/links/gases/pbar.gif
Monometer: a device for measuring the pressure of a gas in a
container. The pressure of the gas is equal to h (the difference in
mercury levels) in units of mmHg
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Units of Pressure In S.I. units, pressure is measured in pascals
(Pa) Standard Atmospheric Pressure = 1 atmosphere = 101.3 kPa = 760
mm Hg or torr
Gas Conversions Convert: 72.9cm Hg to kilopascals and
atmospheres: (a) to kilopascals
72.9 cm Hg x 10 = 729 mm Hg 729 mm Hg x 101.3 kPa = 97.2 kPa 760
mm Hg (b) to atm 97.2 kPa x 1 atm = 0.960 atm 101.3 kPa eg)
Yesterday, the atmospheric pressure was 103.55kPa. Convert this to
mmHg and to atm.
Units of Temperature Converting between Kelvin and Celsius: K =
oC + 273 Convert the following: _______ oC = 298 K 100 oC = _______
K -147oC = ______K Zero Kelvin is also known as
_________________________________________________________________
This is the temperature where
_______________________________________________________________
Standard Temperature and Pressure: STP The conditions at STP
are: The molar volume of a gas is: Problem: What volume does 35
moles of N2 occupy at STP? Statement:
___________________________________________________________________________
Problem: What is the mass of 4.55L of oxygen gas at STP? Statement:
________________________________________________________________________
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Properties of Gases (Zumdahl 13.8) Gases are fluids Gases flow
like __________. Molecules are in constant_____________ and collide
with one another and with the walls of their container. KMT:
Kinetic Molecular Theory (Zumdahl 13.8) The kinetic molecular
theory describes the molecules movement in solids, liquids and
gases. We will focus on the gas part of this theory an ideal gas.
Go to the following link to learn about KMT.
http://tinyurl.com/KMtheory 1. All matter is composed of tiny
_________________________ 2. Particles are in constant
____________________ 3. Temperature (aka. average kinetic energy)
is proportional to ________________________________
K.E. = mv2 where m= mass v= speed Increasing the temperature
increases the kinetic energy of the molecules. 4. Solids, liquids
and gases differ in the _________________ of motion of their
particles and the extent to which the particles
______________________. Look over the information on solids and
liquids but fill in the following notes on gases. 1. Gases have a
low density Volume of the molecules are SO (small/large)
___________ they can be almost ignored compared with the total
volume of the container. 2. Gases are highly compressible The
volume occupied by a gas is almost entirely _______________
applying pressure pushes the gas molecules closer together reducing
the volume. 3. Collisions are elastic no energy loss in a
collision. No __________________forces between molecules. 4.
Collisions change the _____________ and ________________ of the
particles. Gases completely fill their container Fill in the blank
related to KMT Gas particles are always
(moving/still)________________________ Volume (does/does
not)_______________ take into account the actual volume of the gas
particles Gas pressure is created by:
__________________________________________________________
Collisions are considered (elastic/inelastic)
____________________________________ Increasing temperature causes:
_______________________________________________________ Ideally,
there are (attractions/no attractions) between the gas
particles.
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Gas Laws: We can relate variables of pressure, temperature,
volume and moles of a gas in a variety of ways. These are known as
the Gas Laws, and can be expressed mathematically. Summary (after
reviewing each, you may want to come back and summarize key
equations Boyles Law Charles Law Gay Lusaacs Law Combined Gas Law
Avogadros Law Ideal Gas Law Daltons Law Grahams Law
Boyles Law: The Pressure-Volume Relationship (Zumdahl 13.2) When
the pressure on a sample of gas is increased the volume
_____________ A mathematical expression that describes Boyles Law
is: Sketch of PV graph of Boyles Law: Question: The pressure on a
6.24L sample of gas is increased from 1.04atm to 2.18 atm. What
will be the new volume of the gas (at constant temperature)? Define
variables first: Statement
____________________________________________________________________
Question: If the volume of a sample of gas is 561mL at 1.82 atm,
find its new volume at 1.82 kPa. Define variables first: Statement
____________________________________________________________________
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Charless Law: The Temperature-Volume Relationship (Zumdahl
13.3)
Temperature must always be converted to _______________
Write a mathematical relationship for Charless Law Sketch the
graph of volume versus temperature (in oC) of a gas:
How is absolute zero determined?
Charles Law Question: A 1.50L balloon is heated from 20oC to
80oC at constant pressure. Determine the new volume of the balloon
after it is heated. Define variables: Statement
____________________________________________________________________________
Pressure/Temperature Law (Gay Lussacs Law) When the temperature
on a sample of gas is increased the pressure _____________ A
mathematical expression that describes Gay Lussacs Law is: Sketch
of graph:
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Gay Lussacs Law Question: A solid metal sphere with a volume of
0.750L at a pressure of 600torr, is heated from 15.0oC to 75.5oC.
Determine the new pressure in torr and kPa. Define variables:
Statement
____________________________________________________________________________
Combined Gas Law: Write the mathematical relationship for the
combined gas law: Question: A 2.0L weather balloon at 25.0oC and
1.035atm pressure is released into the atmosphere. As it rises, the
pressure drops to 0.684atm and the temperature drops to 14.0oC.
What is the volume of the balloon? Statement
____________________________________________________________________________
Avogadros Principle (Zumdahl 13.4) At conditions of constant
temperature and pressure, the volume of a sample of ideal gas is
_____________ proportional to the number of moles of gas present A
mathematical expression that summarizes Avogadros Law is: Question:
If 0.214 mol of argon gas occupies a volume of 652 mL at a
particular temperature and pressure, what volume would 0.375 mol of
argon have under the same conditions?
Avogadros Law of Combining Volumes Avogadros principle states
that volume and number of particles are ______________
proportional. In the formation of ammonia, 3 moles of hydrogen
combines in a ratio with 1 mole of nitrogen to form 2 moles of
ammonia: 3H2(g) + N2(g) 2NH3(g) n=3moles n=1 mole n=2 moles
Therefore: 3H2(g) + N2(g) 2NH3(g) At STP V= 3(22.4L) V= 1(22.4L) V=
2 (22.4L)
V= 67.2L V=22.4L V=44.8L
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Question: In the reaction where gaseous nitrogen and gaseous
chlorine combine to produce gaseous nitrogen trichloride, determine
the volume of reactants needed to produce 10L of nitrogen chloride,
under similar conditions. Question: In the production of ammonia
from hydrogen and nitrogen gases,
a) What volume of Nitrogen is needed to react completely with
3.69L of hydrogen gas?
b) What volume of ammonia will form?
Ideal Gas Law (Zumdahl 13.5) Write the formula for the Ideal Gas
Law The Gas Constant (R) Question: What is the pressure (in kPa) of
3.19moles of argon gas in a 15.32L container at 39oC? Statement:
___________________________________________________________________________
Question: At what temperature does a 16.3 g sample of nitrogen gas
have a pressure of 1.25atm in a 25.0L tank? Statement:
___________________________________________________________________________
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Gas Stoichiometry (Zumdahl 13.10) Problem: Consider the
following unbalanced chemical equation for the decomposition of
nitrogen triiodide
NI3(s) N2(g) + I2(s) What volume of nitrogen gas is produced at
27oC and 659 mm Hg if 1.24 g of nitrogen triiodide decomposes?
(Molar mass of NI3 = 394.74gmol)
Statement:
___________________________________________________________________________
Problem: Consider the equation:
CaCO3(s) CaO(s) + CO2(g) a) What volume of CO2 collected at 55oC
and a pressure of 99.0kPa is produced by complete
decomposition of 10.01 g of CaCO3? (Molar mass of CaCO3=
100.09g/mol) Statement:
___________________________________________________________________________
b) What volume of gas is collected at STP by the complete
decomposition of 10.01 g of CaCO3? (use moles from part a))
Statement:
___________________________________________________________________________
Problem: Consider the following unbalanced chemical equation: Si(s)
+ N2(g) Si3N4(s) If 90.35L of nitrogen gas, measured at 100oC and
1.055 atm , is reacted with 115g of Si, what mass of Si3N4 is
formed? (Molar mass of Si3N4 = 140.31g/mol) Statement:
___________________________________________________________________________
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Problem: If in the reaction where 2.5L of nitrogen gas reacts
with 4.22 L of oxygen gas to produce 155L of dinitrogen pentoxide
according to the reaction: N2(g) + O2(g) N2O5 (g)
a) Determine the limiting reactant.
b) Determine the volume of excess reactant remaining.
c) Determine the percent yield.
Daltons Law of Partial Pressure (Zumdahl 13.6) (see more
detailed handouts regarding mole fraction and partial pressures) In
a gas mixture, what is meant by the partial pressure of each gas?
Write the equation for Daltons Law Mole Fraction: Moles A Total
Moles Problem: A container contains 3 different gases A, B and
C.
a) If the partial pressure of A is 1.43atm, B is 3.89atm and C
is 0.47atm, then what is the total pressure? Statement:
___________________________________________________________________________
b) Which gas contains the most particles? How could you express
this as a fraction? Statement:
___________________________________________________________________________
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Problem: If 4.0g oxygen and 4.0 g helium are placed in a 5.0L
vessel at 65oC, what will be the partial pressure of each gas and
what will be the total pressure? Statement:
__________________________________________________________________________
Problem: A tank contains a mixture of 3.0 mol of N2, 2.0 mol O2,
and 1.0 mol of CO2 at 25
oC and a total pressure of 10.0 atm. Calculate the partial
pressure (in atm) for each gas in the mixture. Statement:
_____________________________________________________________________
Vapor Pressure:
http://www.chem.neu.edu/Courses/1131Tom/Lecture11/img005.GIF
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http://www.practicalchemistry.org/data/images/originals/combustion-of-hydrogen-in-air-298.jpg
When gas is collected over water, water vapor is also formed and
mixed with the gas collected. That is why we use the equation: The
water pressure is a constant and is related to temperature. You can
look this up in a table.
In order for the total pressure to equal the atmospheric
pressure, the water level in the gas collecting container must be
_______________________ with the water in the container/trough. A
500. mL sample of H2 gas at 24
oC was prepared by the reaction of iron with hydrochloric acid.
2Fe(s) + 6HCl(aq) 2FeCl3 (aq) + 3H2(g)
The hydrogen thus prepared was collected by displacement of
water. The total pressure of gas collected was 755mmHg.
a) What is the partial pressure of H2 in the mixture? b) How
many moles of H2 are in the mixture? c) How many grams of iron
metal reacted?