DO NOW:

Balance the following equation: ___ Cu + ___ N2 ___ Cu3N

How many atoms of copper will react with 33.9 L of nitrogen at STP to produce copper(I)nitride?

Unit: Gas LawsIntroduction

Notes

After today you will be able to…

• Explain the factors that affect gas pressure• Describe real-world experiences

and how they relate to gas pressure, temperature, and volume• Convert between variable units of

pressure, temperature, and volume• Predict the behavior of a gas by

changing one of its variables

Kinetic Molecular Theory

KMT makes three major assumptions about the particles in a gas:1. Their particles move in a straight line

until they collide with other particles or the walls of their container.

2. The motion of the particles is constant and random.

3. There are no attractive or repulsive forces among the particles.

Kinetic Molecular Theory

Four variables are generally used to describe a gas.1. Pressure (kPa, mmHg, atm)2. Volume (L or mL)3. Temperature (always in Kelvin!)4. Amount (moles)

Pressure1 atm = 760 mm Hg =

101.3 kPa

Use the above conversion factor to convert between

different pressure units when working with gas

laws!

Pressure Conversion Example:

How many atm are in 875 kPa?

875 kPa x __1 atm__101.3 kPa

= 8.64 atm

Pressure Conversion Example:

How many atm are in 1285 mm Hg?

1285 mm Hg x __1 atm__ 760 mm Hg

= 1.691 atm

Temperature

0⁰C = 273 K

Use the above conversion factor to convert between ⁰C and Kelvin when working with gas

laws!

Temperature Conversion Example:

Convert 578 K to ⁰C.

578 K – 273 = 305 ⁰C

Temperature Conversion Example:

Convert 685 ⁰C to K.

685 ⁰C + 273 = 958 K

Amount (moles)

Remember… in order to convert between grams &

moles, we look at the periodic table to calculate

molar mass!

Amount (moles) Conversion Example:

How many moles are in 25.0 g of H₂O?

25.0 g H₂O x __1 mole__ 18.0 g H₂O

= 1.39 mol H₂O

Amount (moles) Conversion Example:

Convert 32.0 g K₂O to moles.

32.0 g K₂O x __1 mole__ 94.2 g K₂O

= 0.340 mol K₂O

Factors Affecting Gas Pressure

Effect of adding or removing gas:•When the amount of gas in a given volume is increased, pressure increases.•Example: Doubling amount of gas

= gas particle

2x Amount of gas,

2x Pressure

Factors Affecting Gas Pressure

•More particles means more collisions, which means more pressure!•This is a direct relationship: If the number of particles double, pressure doubles.

Real-World Application: Whitewater Rafting!

The strength and flexibility of the raft are important when you go whitewater rafting.• Think about it! The raft must be able to

withstand the pressure of the air inside the raft and the force of the rapids below.

• If the raft is too inflated (too much gas is added) the raft will easily burst.

• But if not enough gas is added, the raft will not stay afloat!

Factors Affecting Gas Pressure

Effect of changing volume of container:•When the volume of a gas is decreased (for a given amount of gas) pressure increases.•Example: Decreasing volume by half= gas

particle

½ Volume, 2x Pressure

Factors Affecting Gas Pressure

•Particles are closer together in a container which means more collisions which really means more pressure!•This is an indirect relationship: If the volume is halved, pressure is doubled and vice-versa.

Real-World Application:Opening Soda Cans and BottlesSoda cans or bottles are usually opened slowly because we’ve learned that popping them open too fast causes it to fizz up and spill all over the place!• When you open the cap, the gas is suddenly

able to increase its volume in order to decrease the pressure inside the can.

• Shaking a carbonated beverage causes the gas bubbles to mix with the soda and before some of the gas can settle out, you’ve got quite the mess now don’t you?

Factors Affecting Gas Pressure

Effect of changing temperature of a gas:•When the temperature of a gas increases the particles have more KE, and pressure increases.•Example: Doubling temperature = gas

particle

298K 596K2x

Temperature, 2x Pressure

Factors Affecting Gas Pressure

•The particles move faster when heated, and strike the walls of the container with more force, so the pressure builds.•This is a direct relationship: If the temperature is doubled, pressure is doubled and vice-versa.

Real-World Application:Aerosol Cans

A gas in a sealed container can generate an enormous amount of pressure when heated.• That’s why all labels on aerosol cans say

“DO NOT STORE ABOVE 120°F.”• Even “empty” aerosol cans still have some

gas in them, so they will explode if thrown into a fire.

• It is also wise to not store cans at temperatures that will freeze the substances in them. Freezing causes the substance to expand and will puncture the can.

Questions? Complete WS

Your Exit Ticket PRACTICE - To Be Handed in BEFORE You Leave Today!

ANSWER AT LEAST 4!!!!

1) Identify all 5 variables involved in the gas laws! Identify all units associated with each variable!

2) Convert 1125 mm Hg to atm.

3) Convert 1.46 atm to kPa.

4) Convert 0.785 atm to mm Hg.

5) Convert 893 kPa to atm.

6) Convert 475 K to ⁰C.