Agenda: 4/22

• Gases & Gas Laws• Purpose: To use mathematical formulas to predict how a gas will change

• Warm-up: Stoichiometry Problems with Gases• States of Matter• Kinetic Molecular Theory• Measurements used in Gas

3

Essential to Stoichiometry Set-up of problems

Given: Amount &

Unit

Do I need to convert the

given to moles?

Mole Ratio Do I need to convert from

moles to another unit?

Unknown:Unit

The mole ratio is the heart of the stoichiometry calculation

Stoichiometry Calculations

4

Mole Ratio

Mole________Mole

Mole Mole

X

Mass Volume of a Gas

Particles

Volume of a Gas

Mass

Particles

Stoichiometry Problem• To produce ammonia, nitrogen gas reacts with hydrogen

gas. • Write the balanced chemical equation:

• Calculate: • How many liters of ammonia will be produced if there are

10 moles of nitrogen gas (and plenty of hydrogen gas for the reaction to proceed)?

• How many liters of hydrogen gas will be needed to react with 25 liters of nitrogen gas?

GASESUnit 8

Essential Standards: 2.1.5

Chapters 13 & 14

Purpose: To use mathematical formulas to predict how a gas will change

GAS LAWS (FORMULAS)

-Gas molecules act in orderly and predictable ways.

- We can use mathematical formulas to predict what they will do when we change Temperature,

Pressure, or Amount.

Review: What are gases? Describe the location & movement of the particles at each state of matter?

How are gases different?

What are gases? How are they different?Describe the gases in terms of size and type of compound (bond type).

Elements that exist as gases at 250C and 1 atmosphere

Differentiating gases from solids and liquids

• Kinetic Molecular Theory• or “Why solids, liquids and gases behave as they do”

• How are gases different?

Differentiating gases from solids and liquids• Kinetic Molecular Theory

• or “Why solids, liquids and gases behave as they do”

• All matter is made of __________________and these are always in _________________. - Temperature determines the ____________of the ___________________.There are 3 states of matter on earth: _______,________________, __________________.

Gas Behavior – Kinetic Molecular Theory

• http://ed.ted.com/lessons/describing-the-invisible-properties-of-gas-brian-bennett

• 5 characteristics of gases

1. -

2. -

3. -

4. -

5. -

http://education-portal.com/academy/lesson/the-kinetic-molecular-theory-properties-of-gases.html#lesson

Chemical particles (atoms, molecules, or compounds) act differently when they are in different states of matter

PHET – States of Matter – Basicshttps://phet.colorado.edu/en/simulation/states-of-matter-basicsAnimation – http://www.pbs.org/wgbh/nova/physics/states-of-matter.htmlIncludes Temperature & Pressure; Water, Carbon dioxide and hydrogen gas

animationsHeating curveKMT- SolidKMT-Liquid KMT- Gas

Ways we measure gases:

Abbreviation Measurement

Volume

Temperature

Number or quantity – atoms or molecules

Pressure

Gas Temperature: Always use Kelvin

Celcius Kelvin

Temperature Conversions

• Convert 25.0℃ to Kelvin

• Convert 375K to ℃

• Convert -50℃ to K

Pressure • http://www.dlt.ncssm.edu/Tiger/chem3.htm• http://

education-portal.com/academy/lesson/pressure-and-temperature-conversions.html#lesson

AnimationAtmospheric pressure

You Tube – Atmospheric Pressurehttp://www.youtube.com/watch?v=xJHJsA7bYGc

Sea level 1 atm

4 miles 0.5 atm

10 miles 0.2 atm

Air Pressure of the Atmosphere

Units of Pressure

1 atm = 760 mmHg = 760 torr

1 atm = 101 kPa (101,325 Pa)

Barometer

Pressure = ForceArea

Or 760 mm of Mercury

Measuring Pressure: UnitsUnit Unit name STP:

Measurement at sea level & 0°C

Mm Hg Mm Mercury 760 mm Hg

Atm atomospheres 1 atm

kPa kiloPascals 101 kPa

Torr Torr 760 torr

PSI*Tire pressure

Pounds per square inch

14.7 psi

STP = Standard Temperature & PressureWhat does the chemistry reference table tell you? • STP= 1 atm at 0°C or _________ K• = __________mm Hg• = __________ KPa• = __________ torr

Standard Molar Volume of a Gas: 1 mole = ______ Liter(volume occupied by one mole of any gasat STP = ______ Liter)

Pressure Conversions

• Convert 98.35 kPa to atm

• Convert 745 mm Hg to atm

• Convert 740 mm Hg to kPa

GAS LAWSShows the relationship of volume. Temperature, pressure and quantity of molecules in mathematical terms

Gases act in predictable ways so we can use

mathematical formulas to determine how they act

http://phet.colorado.edu/en/simulation/gas-properties

Three Major Laws

Combined Gas Law

P₁V₁= P₂V₂ T₁ T₂

Ideal Gas Law

PV = nRT

•Dalton’s Law of Partial Pressure

Ptotal = P₁+P₂+P₃+Petc.

“A Rational Equation” means an equation which uses ________.

Isolating the Unknown Variable

P₁V₁ = P₂V₂ T₁ T₂

We can slide diagonally across the equal sign without changing the mathematical relationship.

Need variable cards

Isolating the Unknown Variable

P₁V₁ = P₂V₂ T₁ T₂

We can slide diagonally across the equal sign without changing the mathematical relationship.

Isolating the Unknown Variable

P₁V₁ = P₂V₂ T₁ T₂

We can slide diagonally across the equal sign without changing the mathematical relationship.

Isolating the Unknown Variable

P₁V₁ = P₂V₂ T₁ T₂

We can slide diagonally across the equal sign without changing the mathematical relationship.

Combined Gas Law

Combined Gas Law

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

Combined Gas Law: Example

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

A gas at 110 kPa and 30℃ fills a flexible container with an initial volumeOf 2.00L. If the temperature is raised to 80℃ and the pressure increasedTo 440 kPa, what is the new volume?

Answer: 0.58L

Constant variable Changing variables Law

Temperature Boyles

Pressure Charles

Volume Gay-Lussac

Combined Gas Law P₁V₁= P₂V₂ T₁ T₂

Keeping one variable constant:

Boyles’ Law Animation• http://

group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/gaslaw/boyles_law_graph.html

Boyles’ Law: Vary P & VUses: bicycle pump; syringe for injections; popping a balloon by squeezing; Scuba diving: increase in bubble size as rise to surface of water Others?

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

Boyles’ Law: ExampleA cylinder of oxygen has a volume of 2.0L. The pressure of the gas is 10 atm at 0℃. What will be the volume at STP?

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

Boyles’ Law: Practice Problems

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

Boyles’ Law: Practice Problems

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

Charles’ Law – animation

• http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/gaslaw/charles_law.html

http://phet.colorado.edu/en/simulation/gas-properties

Charles’ Law: Vary V & TUses: Hot Air Balloons

Decorating with party balloons; Cooked turkey monitor/device; Playing basketball on a cold day

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

Charles’ Law: Practice Problems

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

Charles’ Law: Practice Problems

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

Gay Lussac’s Law: Vary P and TUses: Heating cans (soup, spray); Pop corn;

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

http://phet.colorado.edu/en/simulation/gas-properties

Gay Lussac’s Law: Practice Problems

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

Gay Lussac’s Law: Practice Problems

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

COMBINED GAS LAW

Combined Gas Law

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

A balloon is partially filled with helium on the ground in the mountains (temp.is 22°C and the pressure is 740 torr. At these conditions, the volume is 10 m³.If released, what would be the volume in m³ at an altitude 5300 m where the pressure is 370 torr and the temperature is - 23°C?

Combined Gas Law

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

The volume of a gas is 27.5 mL at 22°C and 0.974 atm. What will the volume be at 15°C and 0.993 atm?

Combined Gas Law

Initial condition(1) Final condition (2)

Pressure

Volume

Temp. K

P₁V₁ = P₂V₂ T₁ T₂

A 700 mL gas sample at STP is compressed to a volumeof 200mL and the temperature is increased to 30°C. What is the new pressure of the gas?

P₁ V₁ T₁ P₂ V₂ T₂

1.5 atm 3.0L 20°C 2.5 atm ? 30°C

Combined Gas Law

Ideal Gas LawUse when________ is included.

• Formula: PV = nRT

P =

V=

n=

R= 0.0821 L∙atm

mol∙K

T=

Ideal Gas Law• Formula: PV = nRTWhat is the pressure exerted by a 0.5 mol sample of N₂ gas in a 10L container at 278K?

P = V= n= R= 0.0821 L∙atm mol∙KT=

Ideal Gas Law

• Formula: PV = nRTHow many moles of O₂ will occupy a volume of 2.5L at 1.2 atm and 25°C?

P = V= n= R= 0.0821 L∙atm mol∙KT=

Ideal Gas Law: PV = nRTWhat volume will 2 mol of N₂ gas occupy at 720 torr and 20°C?

P = V= n= R= 0.0821 L∙atm mol∙KT=

Ideal Gas Law: PV = nRTAt what temperature will 5 grams of Cl₂ gas exert with a pressure of 900 mm Hg and volume of 750 mL?

P = V= n= R= 0.0821 L∙atm mol∙KT=

Dalton’s Law of Partial Pressure

• Mixture of gases (no reaction takes place)

• What is the total blood gas pressure for a person having CO₂ partial pressure of 60.1 mm Hg and an O₂ partial pressure of 39.2 mm Hg?

Ptotal = P₁+P₂+P₃+Petc.

Dalton’s Law of Partial Pressures

V and T are

constant

P1 P2 Ptotal = P1 + P2

Avogadro’s Law

V a number of moles (n)

V = constant x n

V1/n1 = V2/n2

Constant temperatureConstant pressure

• Animation – • http://

www.pbs.org/wgbh/nova/physics/states-of-matter.html• Includes Temperature & Pressure; Water, Carbon dioxide

and hydrogen gas

• DiscoveryEd video: Kinetic Molecular Theory• Kinetic_Molecular_Theory.wmv

• http://education-portal.com/academy/course/general-chemistry-course.html