Chapter 6: the gaseous state Flashcards
(157 cards)
1
Q
gases have similar .., which allows us to develop models to predict their …
A
physical behaviors; properties
2
Q
a gas is a fluid with no definite … or fixed …
A
shape; volume
3
Q
a gas fills the
A
total volume of its container
4
Q
because a gas is mostly empty space, a gas is
A
compressible
5
Q
the volume of a gas … when an external force is applied
A
decreases
6
Q
a liquid is a fluid with a
A
fixed volume but no definite shape
7
Q
a liquid takes the …., but it does not…
A
shape of its container; expand to fill the container
8
Q
a solid has both fixed … and …
A
shape; volume
9
Q
liquids and solids are …
A
condensed phases
10
Q
condensed phases: phases that are resistant to … because the spaces between the particles are … and cannot ….
A
volume changes; small; readily change
11
Q
because the individual particles in both the liquid and solid phases are …., but in the gas phase are …, the density of the gas phase is much … than the density of either of the condensed phases
A
closely packed; separated; lower
12
Q
density is generally expressed in .. for a gas, but the densities of liquids and solids are expressed in …
A
grams per liter; grams per milliliter
13
Q
when a gas under atmospheric conditions condenses to a solid or a liquid, the density increases by a fact of about
A
1000
14
Q
liquids and solids are resistant to volume changes because the spaces between the particles are
A
small and cannot readily change
15
Q
pressure is defined as the
A
force exerted on a surface divided by the area of the surface
16
Q
the atmosphere exerts a pressure because of the
A
weight of the gas molecules in the air
17
Q
a barometer measures the
A
pressure of the amosphere
18
Q
gravitational attraction pulls down the column of mercury, leaving a … above it in the tube. the column stops falling when the pressure caused by the weight of the mercury is
A
vacuum; equal to the pressure exerted by the atmosphere
19
Q
mercury level in barometer rises→
A
high pressure
20
Q
mercury level in barometer lowers→
A
low pressure
21
Q
mercury is used in barometers because it is a liquid with a
A
high density
22
Q
a manometer measures pressure
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differences
23
Q
(manometer) the atmosphere exerts a … on the mercury surface at the open end of the tube, and the gas within the container exerts pressure on the …
A
pressure; other surface of the mercury
24
Q
(manometer) the difference between the heights of the 2 mercury surfaces corresponds to the difference between the
A
gas pressure in the container and the atmospheric pressure
25
for a closed-end manometer the pressure of the gas is ... to the difference between the heights of the ...
equal; two mercury surfaces
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si unit for pressure
pascal
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1 pa = 1 N/ m^2 =
1 kg/ m * s^2
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1 bar =
10^5 Pa
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1 atm= ... mm Hg
760
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1 torr = ... Pa
133.3
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1 atm= ... torr
760
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1 atm= ... psi
14.7
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psi is
pounds per square inch
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1 atm= ... kPa
101.325
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1 atm= ... bar
1.01325
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1 atm= .... in Hg
29.92
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the physical properties of all gases behave in the ..., regardless of the ...
same general manner; identity of the gas
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4 independent properties that define the physical state of a gas:
pressure; volume; temperature; number of moles
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gas laws express the relationships between the
4 independent properties of gases
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volume of a gas increases as pressure
decreases
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boyle's law states that at constant ..., the ... of a sample of gas is ... proportional to the ...
temperature; volume; inversely; pressure
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V=
constant X 1/P
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PV=
constant
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P1V1=
P2V2
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doubling the temperature causes the volume of the gas to
double
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charles's law states that at constant ..., the ... of a fixed amount of gas is ... to the absolute ...
pressure; volume; directly proportional; temperature
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V = (charles's law)
constant * T
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at absolute zero the volume of the gas must be
zero
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at absolute zero the volume of gas is zero because all gases .... before they reach this temperature
condense to liquid/solid phase
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absolute zero: ... degrees C; ... K
-273.15; 0
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V/T =
constant
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V1/T1=
V2/T2
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avogadro proposed that at thes ame temperature and pressure, equal volumes of gases contain the
same number of particles
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avogadro;s law states that at constant pressure and temperature, the volume of a gas sample is ...
proportional to the number of moles of gas present
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(avogadro's law) V=
constant * n
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V1/n1 =
V2/n2
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combined gas law:
P1V1/n1 = P2V2/n2
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temps must be expressed in
kelvins
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R with units L*atm/ mol*K
0.08206
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R with units kg*m^2/s^2*mol*K
8.314
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R with units J/mol*K
8.314
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R with units cal/mol*K
1.987
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SCUBA:
self-contained underwater breathing apparatus
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high pressures caused by water at depths greater than ... starts to force more nitrogen gas to .... leading to a state of motor function loss, decision making inability, and impairment in judgment known as ...
50 m; dissolve into the bloodstream and other tissues; nitrogen narcosis
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the bends: a diver ascends toward the surface too quickly and nitrogen .... which then collect in the ... causing extreme pain and the body ...
bubbles come out of the body tissues; joints; curls up
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reaction in air bags
decomposition of sodium azide
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divers use an air mix that contains a lot of ... gas, because helium doesn't ...
helium; dissolve in body tissues to a large extent
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divers can also use air mixes that contain ..., but this can cause ..., which thus results in uncontrollable ...
heliox; high-pressure nervous syndrome; shaking
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trimix: mixture of ... o2, ... n2, and ... He
10%; 20%; 70%
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ideal gas law:
PV=nRT
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R is the
ideal gas constant
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the value of the constant R is determined
experimentally
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measurements show that the volume of 1 mol of an ideal gas at standard temperature and pressure is
22.41 L
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standard temperature and pressure:
1 atm; 0 degrees C/273K
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the ideal gas law expresses the interrelationships of
volume, pressure, amount, and temperature
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we use the term ideal because under certain conditions the behavior of gases
deviates from that predicted by the ideal gas law
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the idea gas law is used to determine the value of any of the four properties--...., given values of the other three
pressure, volume, amount, and temperature of a gas
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before the development of mass spectrometry, the molar masses of many substances were determined by using the
ideal gas law
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the ... of any given gas under a fixed set of conditions is also calculated from the ideal gas law
density
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at constant pressure and temperature, the density of a gas is directly related to its
molar mass
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just as in solution, reacting species in the gas phase can readily ..., a necessary requireent for reactions to occur
collide
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use the ideal gas law to convert the moles of a gas sample to its
equivalent volume
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in chemical reactions at constant temp and pressure, the volumes of gases combine in the
same proportions as the coefficients of the equation
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we can directly calculate the volume of a gas produced b a reaction of gases in a chemical reaction, as long as the
pressure and temperaure of the gases are the same
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we do not need a pue sample of gas to use the
ideal gas law
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many of the early experiments that led to the formulation of the gas laws were performed with samples of
air rather than pure substances
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In 1801, English scientist John dalton realized that each gas in a mixture of gases exerts a pressure, called a ..., which is the same as if the gas...
Partial pressure; occupied the container by itself
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Dalton's law of partial pressure:
Pt = Pa + Pb
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A mixture of gases is a
Solution
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A convenient concentration unit to describe this gaseous mixture is the
Mole fraction
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Mole fraction: the number of moles of one component of a mixture divided by
The total number of moles of all substances present in the mixture
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χa =
Moles of component A/ total moles of all substances
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χa=
nA/ ntotal
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χa+χb+χc+....+χn=
1
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Pa =
χa x Pt
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chemists measure the volume of a gas generated in a reaction by
determining the volume of water displaced
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the gas sample collected by displacement of water is not pure, because some
water molecules are also present in the gas phase
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the partial pressure of water present in the gas phase depends on the
temperature of the water
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to determine the partial pressure of the gas collected, you must subtract the partial pressure of the water vapor from the
total pressure
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scientists made measurements of volumes and temperatures of gases to show that the volume of a gas at constant pressure is
proportional to its temperature in kelvins
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chemists sought to understand why a single law can describe the physical behavior of
all gases, regardless of the nature/size of the gas particles
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kinetic molecular theory describes the
behavior of gas particles at the molecular level
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(4 postulates of kinetic theory) a gas consists of ... that are in ... and .... no .... exist between any two gas particles
small particles; constant; random motion; forces of attraction or repulsion
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(4 postulates of kinetic theory) gas particles are very ... compared with the ....
small; average distance that separates them
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(4 postulates of kinetic theory) collisions of gas particles with ... and with the .... are ...
each other; walls of the container; elastic
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(4 postulates of kinetic theory) elastic: no loss in ... when ...
total kinetic energy; particles collide
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(4 postulates of kinetic theory) the average kinetic energy of gas particles is proportional to the
temperature on the kelvin scale
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(kinetic molecular theory) the particles occupy only a small part of the ....; most of the ... is ...
volume of the container; volume; empty space
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(kinetic molecular theory) the gas particles are in
constant motion
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(kinetic molecular theory) the ... and ... of the particles change when they collide, but the ... does not change
direction; speed; total energy of the gas
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(kinetic molecular theory) the energy of the gas changes only if the
temperature changes
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(kinetic molecular theory) the kinetic molecular theory assumes that the pressure exerted by a gas comes from the
collisions of the individual gas particles with the walls of the container
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(kinetic molecular theory) pressure increases if the ... or .... increases, because both will increase the ... on the wall
energy of the collisions; the number of wall collisions per second; force
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the kinetic molecular theory is consistent with the
ideal gas law
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as the size of a container decreases (at constant temperature), the number of ... of the gas particles with the .... during any time interval ..., because the particles have less ... between collisions with the walls
collisions; walls per unit area; increases; distance to travel
116
at constant temperature, the average force of each collision ..., but in a smaller volume, the same number of particles strike a given area of the wall ..., so the pressure of gas in the container ...
does not change; more often; increases as volume decreases
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with an increase in temp and thus an increase in kinetic energy, each collision exerts a ..., and the number of collisions per unit area per time ...
greater force on the walls; increasese
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if pressure is to remain constant, the size of the container must ..., reducing the number of these more ...
increase; energetic collisions per unit area
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increasing the number of gas particles in a container increases the
number of collisions with the walls per unit area per unit time
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not all gas particles move at the same
speed
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the relationship of the average kinetic energy of the gas particles to the speed (u) of the particles is:
KE= 1/2mu^2
| note: KE and u have lines over them, indicating that they are averages
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the square root of u^2 (u with a line over it) is called the ..., labeled ..., and is used to indicate the ...
root-mean-square (rms) speed; urms; average speed of a gas
123
from the mathematical treatment of the kinetic theory of gases, we can determine the
relative number of gas particles that have any particular speed
124
root mean square speed is not the same as the
most probable speed (maximum of graph)
125
plots that show speed and number of particles:
maxwell-boltzmann distribution curves
126
if the temperature increases, the ... increases, the curve ..., and both the most probable speed and urms shift to ...
average speed; broadens; greater values
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the average kinetic energy of the gas particles is proportional to the .., and kinetic molecular theory predicts that the rms speed is related to ... and ... by the equation:
temperature; temperature; molar mass;
| urms=√(3RT)/M
128
R in the urms calculation is
8.314 J/molK
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molar mass in urms is expressed n
kilograms per mole
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the rms speed of a gas sample is proportional to the square root of ... and inverely proportion al to the square root of ...
temperature; molar mass
131
at constant temp, gases with greater maolar masses ave lower
rms speeds
132
the observation that heavier particles have lower rms speeds is expected because the molecules in a heavier sample must move more ... as thea verage kinetic energies of all gases are the .. at a given temperature
slowly; same
133
diffusion is the
mixing of particles caused by motion
134
the faster the molecular motion, the faster a gas
diffuses
135
the rate of diffusion is always less than the ..., because collisions prevent the particles from ..
rms speed of the gas; moving in a straight line
136
effusion is the passage of a gas through
a small hole into an evacuated space
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graham's law states that the rte of ... of a gas is ... to the square root of its ...
effusion; inversely proportional; molar mass
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the kinetic molecular theory explains graham's law because the rms speed of the gas particles is inversely proportional to the
square root of their molar mass
139
rate of effusion of gas a/ rate of effusion of gas B =
√(molar mass of B/ molar mass of A)
140
gases with greater rates of effusion escape through the hole in
shorter lengths of time
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the time it takes for a gas to effuse, t, is .. to the rate of effusion
inversely proportional
142
most gases obey the ideal gas law quite closely at a pressure o about ... and a temperature well above the ... of the substance
1 atm; boiling point
143
for a gas that follows the ideal gas law, the measured values of PV/nRT graph to a
straight line equalling 1
144
as the pressure increases to high values, ... occur
deviations
145
deviations from the ideal gas law occur under extreme conditions because two of the assumptions of the kinetic molecular theory simply are nto correct when
gas particles are close together
146
these assumptions are: that gas particles are ...; that no ... exist between gas particles
small compared with the distances separating them; attractive forces
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at high pressure, the volume occupied by the individual individual particles is no longer negligible coompared with the
volume of the gas sample
148
when the particle's size is no longer negligibl, the actual volume available for the gas particles to move is
reduced
149
gas particles that are attracted to each other do not ... as ... as predicted, reducing he ... below that predicted by the ideal gas law
strike the wall; hard; pressure
150
as the pressure increases, he particles are forced ..., making this attractive interaction more important because because more gas particles are ...
closer together; close to the one about to hit the wall
151
at very high pressures, the effect of molecular volume is greater than that of
the attractive forces
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a gas deviates from the ideal gas law at ... and ... near the ... and at very high ...
temperatures; pressures; condensation point; high pressures
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the ideal gas law can be modified to include the effects of
attractive forces and the volume occupied by the particles
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van der waals equation: nRT-
(P + an^2/V^2)(V-nb)
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n: number of
moles
156
b: constant that depends on the
size of the gas particles
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a: constant related to the strength of the
attractive forces
