GASES - UNIT WRAP-UP

Review Practice

Stoichiometry

Vapor Pressure

Agenda: 4/27 • Warm-up: Ideal gas law video• Choosing the right gas law formula

• Practice Problems

• Gas Stoichiometry • You Tube Video • Practice problems

• Dalton’s Law of Partial Pressure

• States of Matter - Changes • How do the states of matter change? Why? • Sorting Terms• Read States of Change & write a graphic organizer

Ideal Gas Law: Discovery Ed video

Which formula to use?

• Combined Gas Law • Ideal Gas Law

Practice: Ideal & Combined Gas Laws1. If four moles of a gas at a pressure of 5.4 atmospheres

have a volume of 120 liters, what is the temperature?

2. If I initially have a gas with a pressure of 84 kPa and a temperature of 35 and then I heat it to an additional ℃230 , what will be the new pressure? (Assume the ℃volume of the container is constant.)

• 3. My car has an internal volume of 2600 liters. If the sun heats the care from a temperature of 20 to a temperature ℃of 55 , what will the pressure inside my car be? (Assume ℃that the initial pressure was 760 mm Hg.)

• 4. How many moles of gas (air) are in my car in problem #3?

• 5. A toy balloon which is filled with air has an internal pressure of 1.25 atm and a volume of 2.5 L. If I take the balloon to the bottom of the ocean where the pressure is 95 atm, what will be the new volume?

• 6. How many moles of gas does the toy balloon hold at 1.25 atm, 2.5 L, and 285 K?

Stoichiometry – with gases• You Tube Video

Gas Stoichiometry• N₂ +3H₂→ 2NH₃What is the volume of NH₃ at STP if produced if 25.0 g of N₂ is reacted with an excess of H₂?

2KClO₃→ 2KCl + 3O₂If 5.0 g of KClO₃ is decomposed, what volume of O₂ will be produced at STP?

How many grams of KCl are produced in the above problem?

• Zn + 2HCl → ZnCl₂ + H₂• What volume of hydrogen at STP is produced when 2.5 g of zinc react with an excess of hydrochloric acid?

• 2AlCl₃→ 2Al + 3Cl₂• If 10.0 g of aluminum chloride are decomposed, how many molecules of chloride are produced?

Dalton’s Law of Partial Pressures

V and T are

constant

P1 P2 Ptotal = P1 + P2

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.

Avogadro’s Law

V a number of moles (n)

V = constant x n

V1/n1 = V2/n2

Constant temperatureConstant pressure

How are gases related to solids and liquids?

Characteristics of Solids, Liquids & Gases

• Sort the terms into 3 columns: S, L, G• (Hint: Look for 3 cards with similar wording and determine which

best fits solid, liquid or gas)

• Solid Liquid Gas

Gases vs. Liquids & Solids• Read Study Guide pp. 2 - Changes of State• Prepare a graphic organizer to show the changes of state

and why they happen• Include terms: solid, liquid, gas, heat, heat energy, melting,

boiling, evaporation, forces of attraction, bonds, cool

Most substances, like water, can exist in all three states.

A cloud is made of water vapor, a type of gas.

An iceberg is made of water in solid form.

This glass contains liquid water.

How do solids and liquids differ from gases?

HOW DOES A SUBSTANCE BECOME A GAS?

Changing States (Phase changes)

Solid GasLiquid

Increase Thermal Energy (Heat up)

Decrease Thermal Energy (Cool off)

Melting point

• Melting - change from solid to liquid• Melting point - SPECIFIC temperature when melting occurs.

• Each pure substance has a SPECIFIC melting point.• Examples:• M.P. of Water = 0°C (32°F) • M.P. of Nitrogen = -209.9 °C (-345.81998 °F)• M.P. of Silver = 961.93 °C (1763.474 °F) • M.P. of Carbon = 3500.0 °C (6332.0 °F)

Melting Point

• Particles of a solid vibrate so fast that they break free from their fixed positions.

Solid Liquid

Increasing Thermal Energy

Melting point

Vaporization

• Vaporization – change from liquid to gas• Vaporization happens when particles in a liquid gain

enough energy to form a gas.

GasLiquid

Increasing Thermal Energy

Boiling point

Two Kinds of Vaporization

• Evaporation – vaporization that takes place only on the surface of the liquid

• Boiling – when a liquid changes to a gas BELOW its surface as well as above.

Boiling Point

• Boiling Point – temperature at which a liquid boils• Each pure substance has a SPECIFIC boiling point.

• Examples:• B.P. of Water = 100°C (212°F) • B.P. of Nitrogen = -195.79 °C (-320.42 °F)• B.P. of Silver = 2162 °C (3924 °F) • B.P. of Carbon = 4027 °C (7281 °F)

Boiling Point and Melting Point

-150

-100

-50

0

50

100

150

200WATER – H20

time

Tem

per

atu

re Melting point

Boiling point

As heat increases,

Thermal Energy Added

Tem

pera

ture

Standard Curve for all Substances

• As heat decreases,

WHAT ARE THE CHANGES OF STATE?

GAS

SOLID LIQUID

Deposition

Sublimatio

n

Boiling / Evaporation

Condensation

Freezing

Melting

Which are endothermic?

Which are exothermic?

Energy and change of state (phase changes)

Energy levelEnergy changePhase changesMP/BP

Entropy= degree of disorder

Vapor Pressure

The vapor pressure is the pressure measured when there is an equilibrium between the gas and liquid phases. The rates of condensation and vaporization

are equal.

Vapor pressure • http://www.chem.purdue.edu/gchelp/liquids/vpress.html

• Discovery Ed video

Resources for S, L, G• http://www.kentchemistry.com/links/Matter/

HeatingCurve.htm