ch110 chpt 7 gases ch110 chapter 6: gases kinetic molecular theory pressure gas laws
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CH110 Chpt 7 Gases
CH110 CH110 Chapter 6: GasesChapter 6: Gases
Kinetic Molecular TheoryKinetic Molecular Theory
PressurePressure
Gas LawsGas Laws
CH110 Chpt 7 Gases
SolidSolid
LiquidLiquid
VaporVapor
Slow moving, Slow moving, dense,dense,Fixed shapeFixed shape
Moderate Moderate movement,movement,Dense,Dense,Takes shape of containerTakes shape of container
Fast moving, Fast moving, Low density,Low density,Expands to fill containerExpands to fill container
DensityDensity ShapeShape CompressibilityCompressibility
Small Small compressibility,compressibility,
Very smallVery small heat expansion heat expansion
Large Large compressibility,compressibility,Expands w/ heatExpands w/ heat
SmallSmallcompressibility,compressibility,
Small heat expansionSmall heat expansion
CH110 Chpt 7 Gases
1. All gases are made up of tiny particlestiny particles moving in moving in • straight linesstraight lines • in all directions • at various speeds.
Kinetic molecular theory of GasesKinetic molecular theory of Gases
Model to explain behavior of gases
VaporVapor
CH110 Chpt 7 Gases
3.3. V of a gas V of a gas = V of containerV of container
V of a gas is mostly empty space.
2. Particles far apart have no effect onno effect on each othereach other. (Don’t attract or repel)
Kinetic molecular theoryKinetic molecular theory
CH110 Chpt 7 Gases
Kinetic molecular theory Kinetic molecular theory
4. The ave KE ave KE as the TT
•The The average KE average KE is theis the same same for all for all gases atgases at thethe same T. same T.
TTKEKE
(K.E. (K.E. T) T)
CH110 Chpt 7 Gases
5. Gas molecules exert pressurepressure as they collide with container walls
The The > > thethe # # ofof collisionscollisions (per unit time), (per unit time), thethe > > thethe pressure pressure
Kinetic molecular theoryKinetic molecular theory
CH110 Chpt 7 Gases
PressurePressure= = ForceForce per unit of per unit of Area.Area. Force
AreaAreaPP = = ForceForce
AreaArea
In the atmosphere, molecules of air (NN22, ,
OO22, Ar, H, Ar, H22OO, etc..) are constantly bouncing
off us.
CH110 Chpt 7 Gases
We live at the bottom of an ocean of air
Atmospheric PressureAtmospheric Pressure
Atmosphere:A sea of colorless, odorless gases surrounding the earth
CH110 Chpt 7 Gases
PressurePressureAt At higher elevationshigher elevations, there is , there is less less airair so the so the PP is less is less..
CH110 Chpt 7 Gases
Boiling Point Boiling Point = Temp where molecules = Temp where molecules
overcome atmospheric Pressureovercome atmospheric Pressure
Sea LevelSea Level
760 torr760 torrDenver (5280’)Denver (5280’)630 torr630 torr
Mt. Evans,CO(14,000’)Mt. Evans,CO(14,000’)
Mt. Everest(20,000’)Mt. Everest(20,000’)
467 torr467 torr
270 torr270 torr HH22OOHH22OO
= 100 oC
= 95 oC
= 87 oC
= 73 oC
CH110 Chpt 7 Gases
Measuring PressureMeasuring PressureAttempts to
pump water out of flooded
mines often failed because
HH22O can’t be O can’t be
lifted more than lifted more than 34 feet.34 feet.
CH110 Chpt 7 Gases
Measuring PressureMeasuring PressureTorricelliTorricelli believed reason was that P of atmosphere could not hold anything heavier than a 34’ column of water.
CH110 Chpt 7 Gases
Like drinking from a straw.
What causes the liquid to move up the straw to your mouth ?
Atmospheric Pressure Atmospheric Pressure
CH110 Chpt 7 Gases
34’ columnof water
1 Atm1 Atm
The atmosphere
would support a column of
H2O> 34 feet high.
Measuring PressureMeasuring Pressure
CH110 Chpt 7 Gases
Torricelli BarometerTorricelli BarometerPressure of the atmosphere supports aPressure of the atmosphere supports acolumn of column of Hg 760 mmHg 760 mm high. high.
1 atm
1 atm1 atm =760 mm Hg760 mm Hg760 torr760 torr29.92 in Hg14.7 lb/in2
101,325 Pa
vacuumvacuum
Mercury used because it’s so dense.
CH110 Chpt 7 Gases
Blood pressureBlood pressure (systolic over diastolic):most often in mm Hgmm Hg. (ex. 120/80)120/80)
MeteorologistsMeteorologists refer to pressure systems in mm or inches of Hg. ex. 30.01 in30.01 in
CH110 Chpt 7 Gases
STPSTPStandard Temperature & Standard Temperature & PressurePressure
1 atm
1 atm1 atm =760 mm Hg760 mm Hg760 torr760 torr29.92 in Hg14.7 lb/in2
101,325 Pa
00ooCC
273K273K
CH110 Chpt 7 Gases
Gas lawsGas lawsLaws that show relationships between volume and properties of gases
Boyle’s LawBoyle’s LawCharles’ LawCharles’ LawGay-Lussac’s LawGay-Lussac’s Law
Boyle’s LawBoyle’s LawCharles’ LawCharles’ LawGay-Lussac’s LawGay-Lussac’s Law
Avogadro’s LawAvogadro’s LawDalton’s LawDalton’s LawAvogadro’s LawAvogadro’s LawDalton’s LawDalton’s Law
CombinedCombinedGas LawGas Law
CombinedCombinedGas LawGas Law
CH110 Chpt 7 Gases
V V is is inversely proportionalinversely proportional to to PP
when T is constant.when T is constant.
If P goes downIf P goes downIf P goes downIf P goes down V goes upV goes upV goes upV goes up
PP
VV
PP VV
PP
VV
Boyle’s law: V vs PBoyle’s law: V vs P
CH110 Chpt 7 Gases
PP11 = 1 Atm = 1 AtmPP11 = 1 Atm = 1 Atm
VV11 = =VV11 = = 1 L1 L
PP11VV11 = PP22VV22PP11VV11 = PP22VV22 VV22 = =VV22 = =
PP11VV11 = = VV22
PP22
PP11VV11 = = VV22
PP22
1atm (1L)1atm (1L) = =
0.5 atm0.5 atm
1atm (1L)1atm (1L) = =
0.5 atm0.5 atm2 L2 L
Boyle’s law: V vs PBoyle’s law: V vs P
2 L2 L
PP22 = 0.5 Atm = 0.5 AtmPP22 = 0.5 Atm = 0.5 Atm
CH110 Chpt 7 Gases
1 L1 L
Boyle’s law: V vs PBoyle’s law: V vs P2 L2 L
Drive to Drive to top of mountaintop of mountain - - ears start ears start poppingpopping. .
BreathingBreathing at high altitudes is at high altitudes is more more difficultdifficult because the pressure of O because the pressure of O22 is less.is less.
CH110 Chpt 7 Gases
Charles’s law: V vs TCharles’s law: V vs TThe The volume of a gasvolume of a gas is is directly proportionaldirectly proportional to the to the absolute temperatureabsolute temperature (K). (K).
T V
PP
If T goes upIf T goes upIf T goes upIf T goes up V goes upV goes upV goes upV goes up
CH110 Chpt 7 Gases
VV11 = 125 mL
TT11 = 273 K = 273 K
Charles’s law: V vs TCharles’s law: V vs T VV11 = VV22
TT11 TT22
VV11 = VV22
TT11 TT22
VV22 ==
TT22 = 546 K = 546 K
250 mL250 mL250 mL250 mL
(546K546K))125 mL = 273 K273 K
(546K546K))125 mL = 273 K273 K
TT22VV11 = VV22
TT11
TT22VV11 = VV22
TT11
CH110 Chpt 7 Gases
Gay-Lussac’s Law (PGay-Lussac’s Law (PT)T)
Pressure of a gas Pressure of a gas is is directly proportionaldirectly proportional to to
Absolute Temp (K) when Absolute Temp (K) when Volume is constant Volume is constant
PP11 = PP22
TT11 TT22
PP11 = PP22
TT11 TT22
P T
VV
If P goes upIf P goes upIf P goes upIf P goes up T goes upT goes upT goes upT goes up
CH110 Chpt 7 Gases
Boyle’sBoyle’s
Gay-Lussac’sGay-Lussac’s
Charles’Charles’
PT
VVVV
T VPP
TPP
VVGas LawsGas LawsPP11VV1 1 = P= P22VV22
VV11 = = VV22
TT11 TT22
PP11 = = PP22
TT11 TT22
CH110 Chpt 7 Gases
Boyle’sBoyle’s
Gay-Lussac’sGay-Lussac’s
Charles’Charles’
CombinedCombined
Gas LawGas Law
PT
VVVV
T VPP
TPP
VVGas LawsGas Laws
P1V1
T1
==P2V2
T2
CH110 Chpt 7 Gases
A 10 m3 balloon contains helium on the ground where the temperature is 27ºC and the pressure is 740 torr. Find the volume at an altitude of 5300 m if pressure is 370 mm Hg and temperature is -33 ºC.
P1 = 740 mm
T1 = 27 + 273 = 300 K
V1 = 10 m3
P2 = 370 mm
T2 = -33 + 273 = 240 K
V2 = ?
= 16 m3V2 = (240 K)(740 mm)(10 m3 )
(370 mm) (300 K)
P1V1
T1
==P2V2
T2
T2P1V1
P2 T1
== V2
Combined Gas LawCombined Gas Law
CH110 Chpt 7 Gases
Avogadro’s lawAvogadro’s lawThe The volume of a gas volume of a gas is directly is directly
proportional to the proportional to the number of moleculesnumber of molecules
VV11 = VV22
nn11 nn22
VV11 = VV22
nn11 nn22
More moles of a gas, takes up more space.
CH110 Chpt 7 Gases
At Standard Temperature & Pressure At Standard Temperature & Pressure (STP)(STP)
V of 1 mole of gas = V of 1 mole of gas = 22.4 liters22.4 liters
Equal volumes of gas Equal volumes of gas (at same T and P)(at same T and P)
contain equal numbers of molecules.contain equal numbers of molecules.
Avogadro’s lawAvogadro’s law
At T = 273 KAt T = 273 K (0ºC) P = 1 atm1 atm (760 mm)
1 mol He1 mol He
4 g He4 g He
22.4 L22.4 L
1 mol He1 mol He
4 g He4 g He
22.4 L22.4 L
1 mol N1 mol N22
28 g N28 g N22
22.4 L22.4 L
1 mol N1 mol N22
28 g N28 g N22
22.4 L22.4 L
1 mol CO1 mol CO22
44 g CO44 g CO22
22.4 L22.4 L
1 mol CO1 mol CO22
44 g CO44 g CO22
22.4 L22.4 L
CH110 Chpt 7 Gases
66 g CO2
Example:Example: What volume will What volume will 66 grams66 grams of of
COCO22 occupy at occupy at STPSTP??
1 mole CO2
44 g CO2
22.4 liters22.4 liters
1 mole CO1 mole CO22
= 33.6
STPSTP
L
CH110 Chpt 7 Gases
Dalton’s law of Partial PressuresDalton’s law of Partial Pressures
The total pressure of a gas mix = sum of the partial pressures of each gas.
Pair = PN2 + PO2 + PAr + PCO2 + PH2O
PPTT == PP11 + P + P22 + P + P33 + ..... + .....
Each gas acts independently of the others.Each gas acts independently of the others.
Example: AirExample: Air
CH110 Chpt 7 Gases
Pair = PN2 + PO2 + PCO2 + PH2O = 760 mm
Dalton’s law of Partial PressuresDalton’s law of Partial Pressures
Typical values for Atmospheric airAtmospheric air at 0 ºC (excluding argon):
(594.0mm)(594.0mm) +(160mm)+(160mm) +(5.7mm)=+(5.7mm)=+(0.3mm)+(0.3mm) 760mm760mm
As T of air increases, more H2O enters mix.
exampleexample: at 20 ºC, the PH2O = 18 mm Ptotal (760 mm) can’t change, so other
gases get diluted to make room for the water.
CH110 Chpt 7 Gases
Air moving over warm water Air moving over warm water
has more water in it.has more water in it.
Low pressure Low pressure
is often associated with this air.is often associated with this air.
Typhoons and hurricanes
are associated with very warm, moist air.
Pair = PN2 + PO2 + PCO2 + PH2O = 760 mm
CH110 Chpt 7 Gases
Blood GasesBlood Gases
PPCOCO22 ~ 40 mm Hg ~ 40 mm Hg
Normal PO2 in the air =160 mm.
If drops
< 100 mm,
can’t diffuse into the blood.
Arterial Blood Gases (ABGs)Arterial Blood Gases (ABGs)
PPBGBG = = PPOO22 + + PPCOCO22
PPOO22 ~ 100 mm Hg ~ 100 mm Hg
PCO2 ~ 46 mm Hg
Venous Blood Gases (VBGs)Venous Blood Gases (VBGs)
PO2 ~ 40 mm Hg
CH110 Chpt 7 Gases
We only use about 25% of the OxygenOxygen we inhale.
The rest is exhaled along with the NitrogenNitrogen and some carbon dioxide.
THIS IS WHY CPRCPR WORKS !!!
CH110 Chpt 7 Gases
HENRY’S LAWHENRY’S LAWThe solubility of a gassolubility of a gas in a liquid is directly directly related to the pressurepressure on the liquid.
P SolTT
If P goes upIf P goes upIf P goes upIf P goes up Gas solubility goes upGas solubility goes up(more gas will dissolve)(more gas will dissolve)
Gas solubility goes upGas solubility goes up(more gas will dissolve)(more gas will dissolve)
CH110 Chpt 7 Gases
If P goes downIf P goes downIf P goes downIf P goes down Gas solubility goes downGas solubility goes down(gases escape)(gases escape)
Gas solubility goes downGas solubility goes down(gases escape)(gases escape)
HENRY’S LAWHENRY’S LAW
P SolTT
Soda under high pressure
Soda under low pressure
Example: opening a sodaExample: opening a soda.
CH110 Chpt 7 Gases
The “BendsThe “Bends””
Lots of Lots of dissolved Ndissolved N22
High PHigh P
Less dissolved Less dissolved gasesgases
Lower PLower P
Quick ascent Quick ascent Get bubbles in blood & Get bubbles in blood & joints joints extreme painextreme pain
CH110 Chpt 7 Gases
The “BendsThe “Bends””
Lots of Lots of dissolved gasesdissolved gases
High PHigh P
Less Less dissolved dissolved
gasesgases
Lower PLower PNN22 accumulatesaccumulates in in
brainbrain, , spinal cordspinal cord, , and peripheral and peripheral
nerves. Bubbles here nerves. Bubbles here can can cause paralysis cause paralysis and convulsions.and convulsions.
Effects often Effects often irreversible.irreversible.
NN22 accumulatesaccumulates in in
brainbrain, , spinal cordspinal cord, , and peripheral and peripheral
nerves. Bubbles here nerves. Bubbles here can can cause paralysis cause paralysis and convulsions.and convulsions.
Effects often Effects often irreversible.irreversible.
CH110 Chpt 7 Gases
“Nitrogen Narcosis”,
= nitrogen euphoria or raptures of the deep.
(Effect somewhat like that observed
when alcohol levels rise in the blood.)
So, So, HeliumHelium
often often substitutedsubstituted for for
NN22 in divers air. in divers air.
Nitrogen NarcosisNitrogen Narcosis
CH110 Chpt 7 Gases
The solubility of a gassolubility of a gas in a liquid is inversely inversely related to the temperaturetemperature .
If T goes upIf T goes upIf T goes upIf T goes up Gas solubility goes downGas solubility goes down(gases escape)(gases escape)
Gas solubility goes downGas solubility goes down(gases escape)(gases escape)
Temperature vs SolubilityTemperature vs Solubility
Gas SolubilityGas Solubility
TT
SS
TT SS
TT
SS
CH110 Chpt 7 Gases
Temperature vs SolubilityTemperature vs SolubilityCold HCold H22O holds more gas than warm HO holds more gas than warm H22OO
If hot rivers lose too much dissolved OIf hot rivers lose too much dissolved O22
the fish can’t survive.the fish can’t survive.
CH110 Chpt 7 Gases
Carbonated beverages bottled cold.
Temperature vs SolubilityTemperature vs Solubility
Divers with bends often packed in ice for transport
to hyperbaric chamber.
CH110 Chpt 7 Gases
Gas LawsGas LawsHenry’sHenry’s
SolubilitySolubility
TTPP
PP SolubilitySolubilityTT
T vs SolT vs Sol
CH110 Chpt 7 Gases
Bernoulli's PrincipleBernoulli's Principle
Faster moving gases gases exert less pressurepressure than slow moving gases.
Fast moving Fast moving GasesGases
Fast moving Fast moving GasesGases Low PLow P
Slow moving Slow moving GasesGases
Slow moving Slow moving GasesGases
High PHigh P