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

It all “Boyle’s” down to Breathing in and out.

Boyle’s lawBoyle’s law

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

CH110 Chpt 7 Gases

Bernoulli's PrincipleBernoulli's Principle

Slow moving Slow moving GasesGases

Slow moving Slow moving GasesGases

Fast moving Fast moving GasesGases

Fast moving Fast moving GasesGases

High PHigh P

Low PLow P