Grade 11 Pre-AP Chemistry - Unit 5 Test Review

What is Pressure?

force per unit area

measured in pascals (Pa)

How is Pressure Caused?

when molecules collide into a surface

Kinetic Molecular Theory

unless they hit another particle/edge of the container...

-gas particles move in a straight line

-gas particles stay at a constant speed

-gas particles move in the same direction

Properties of Gases

-indefinite shape/volume

-low density

-low attraction between particles

-colourless/odorless

-gas molecules are always moving

STP Conditions

101.3 kPa and 0 degrees Celsius

SATP Conditions

100 kPa and 25 degrees Celsius

conversions for pressure (other units)

101.3 kPa = 760 mm Hg = 760 torr = 14.696 psi = 1 atm (atmosphere)

barometer

measures atmospheric P

-open dish of Hg with a tube inverted in it

-as air particles collide with the Hg they exert pressure on it

-since the particles in Hg are already close together, they don't compress, they just move

-the Hg moves into the tube

-the more P, the more mm Hg

manometer

measures P of other gases

-u-shaped

-Hg in it sinks to the bottom

-gas enters one side; pushes against Hg, causing it to rise on the other side

-P of gas can be found by the difference in height between the two arms of the manometer

Dalton's Law of Partial Pressure

all partial pressures add up to the total pressure

Ptotal = P1 + P2 + P3 ...

Boyle's Law

when T is constant, P increases as V decreases

P1V1 = P2V2

Charles' Law

when P is constant, V increases as T increases

V1 / T1 = V2 / T2

Gay-Lussac's Law

when V is constant, P increases as T increases

P1 / T1 = P2 / T2

What unit are all T's for gases measured in?

KELVIN

Conversion for T from Celsius to Kelvin

T (in Kelvin) = T (in Celsius) + 273.15

Displacement of Water

method to trap + measure P of a gas

-rxn in the flask to produce the gas you want to know the P of

-as gas is generated, it flows through the rubber tubing and bubbles up through the water into the top of the test tube, where it collects

-as more gas collects, the water gets displaced from the test tube

-once all the water is gone, the test tube contains a sample of your gas (WET GAS)

Wet Gas

gas that has water vapour

How do you find the P of the Dry Gas after Displacing Water?

look up the water vapour P at the T you are doing the experiment at, then:

Pdry gas = Ptotal - PH2O

Combined Gas Law

P1V1 / T1 = P2V2 / T2

Greenhouse Effect

natural process in which gases absorb IR emitted from the Earth's surface and radiate it, heating the atmosphere and Earth's surface

Carbon Sequestration

the process of removing CO2 from the atmosphere and storing it

Two Common Types of Carbon Sequestration

biological - plants used to naturally remove CO2

geological - pumping CO2 into depleted reservoirs

4 Layers of the Atmosphere

troposphere, stratosphere, mesosphere, thermosphere

Troposphere (T vs altitude)

T decreases as altitude increases

Stratosphere (T vs altitude)

T increases as altitude increases

-due to higher concentration of ozone

-trapped energy is released to nearby gas molecules

Mesosphere (T vs altitude)

T decreases as altitude increases

Thermosphere

T increases as altitude increases

-due to gas molecules absorbing radiation from Sun

-in the process, they emit visible radiation in the form of auroras

Composition of the Atmosphere

Nitrogen (around 78%)

Oxygen (around 21%)

Argon (around 0.9%)

CO2, water vapour, etc. (rest)

Major GHGs

CO2, CH4 (methane), and water vapour

CO2

GHG

Methane

GHG

Water Vapour

GHG

GHG

gas in the atmosphere that traps IR and radiates it back towards the Earth, heating it past natural standards

Photochemical Smog

smog that contains ground-level ozone, gases, and fine particles

How is Photochemical Smog Produced?

reaction of vehicle + factory emissions + sunlight

Pollutant Gases

sulfur dioxide

nitrogen oxides

carbon monoxide

Sulfur Dioxide

Pollutant gas

SO2 - results from combustion of fossil fuels containing sulfur impurities; reacts to cause acid precipitation

strong choking odour

Nitrogen Oxides

Pollutant gas

e.g. NO - results from vehicles using fossil fuels; contribute to smog/acid precipitation

causes brownish smog

VOCs

volatile organic compounds

-air pollutants

-solid/liquid carbon-containing cpds that vaporize readily

-contribute to formation of smog

-can depress CNS and cause cancer in larger doses

Example of a VOC

gasoline

Ozone (in the stratosphere)

gas that absorbs dangerous UV radiation from the Sun, keeping the planet habitable

Ozone (in the troposphere)

known as ground-level ozone

pollutant - harmful for human health

can cause respiratory issues

How is Ground-Level Ozone Produced?

nitrogen oxides and VOCs react in the presence of sunlight

Particulate Matter

mixture of solid and liquid particles found in the atmosphere

Examples of Particulate Matter

dust, mold, pollen, soot, ash

How is Particulate Matter Produced?

combustion

AQHI

Air Quality Health Index

-scale used to assess the risk of health effects from air pollution

Off-Gassing

release of gases from a substance at room T (e.g. "new car" smell)

Examples of Chemical Pollutants

Methanal - results from off-gassing of paint/cardboard

Carbon Monoxide

Radon - results from radioactive decay of uranium in soil

Methanal

a VOC and chemical pollutant

colourless, flammable gas with a distinctive sharp odour

Sources of Methanal

-paints

-cosmetics

-wallpaper

-cardboard

Carbon Monoxide

(chemical) Pollutant

results from incomplete combustion

difficult to detect (odourless, colourless)

Radon

chemical pollutant

colourless, odourless gas

produced by radioactive decay of uranium in soil and rock

leading cause of lung cancer for non-smokers

Examples of Biological Pollutants

-bacteria

-viruses

-mites

-dust

-pollen

-mold

-humans (shedding of skin cells which are a major component of dust)

Mole Fraction

add up all the moles, then:

the moles of the specific gas / total moles

A mixture of 3 gases has a P of 980 torr. Calculate the partial P of each gas in kPa if there are 3 mol H2, 2 mol CO2, and 6 mol Ne in the container.

Add up the moles to get total moles:

3 + 2 + 6 = 11 mol

Convert the total P from torr to kPa:

980 torr x 101.3 kPa / 760 torr = 130.6236842 kPa

Find the partial P in kPa:

P H2 = (3 mol / 11 mol) x 130.6236842 kPa = 35.62464115 kPa

P CO2 = (2 mol / 11 mol) x 130.6236842 kPa = 23.74993475 kPa

P Ne = (6 mol / 11 mol) x 130.6236842 kPa = 71.24928229 kPa

Factors Affecting the Volume of a Gas

1. Pressure - as P increases, V decreases

2. Temperature - as T increases, V increases

3. Amount of Particles (moles or n) - as n increases, V increases

Ideal Gas Equation

PV = nRT

R in Ideal Gas Equation

8.314 (kPa)(L) / (mol)(K)

What is an Ideal Gas?

a hypothetical gas in which the particles don't interact at all, all collisions are completely elastic, and all gas laws are followed exactly with V dropping to 0 as T approaches absolute 0

Avogadro's Law

as n increases, V increases

n1 / V1 = n2 / V2

Molar Volume of a Gas at STP

22.4 L

Density Formula

D = P x MM / RT

OR

D = mP / nRT

How do Particles Behave at Absolute 0?

no movement, no thermal energy, V should drop to 0 as T approaches absolute 0

Ideal Gas vs Real Gas

actual gases ARE NOT ideal gases, but they will act like one as long as conditions are not extreme

Differences Between Solids, Liquids and Gases with Kinetic Molecular Theory

Vibrational motion: gases, Liquids and Solids

Rotational motion: gases and Liquids

Translational motion: gases and liquids

Vibrational Motion

vibration of particles

Rotational Motion

a particle spinning in place

Translational Motion

the movement of a particle in straight lines

How is Pressure Affected as Altitude Changes?

higher altitude - lower pressure

lower altitude - higher pressure

What does the graph between P and T look like?

What does the graph between V and T look like?

What does the graph between V and P look like?

N/m^2 and Pa

1 N/m^2 = 1 Pa

Why doesn't it matter what gases are added to a container?

because the particles are so far apart, there is minimal interactions between them, therefore, the gases will behave separately (as long as no chemical reaction occurs)

2 things needed to consider when collecting a gas over water

1. cannot use a gas that dissolves in water

2. the gas will be a 'wet gas' (have to subtract the P of the water vapour in the gas to get the P of the 'dry gas') - using chart

What does it mean when you see the words 'collected over water' in the question?

you need to subtract the water vapour P using Dalton's Law of Partial Pressures

What substance gives smog its reddish-brown colour?

nitrogen dioxide

Nitrogen

most abundant gas in the atmosphere

important in all biological systems

Where is most of the ozone in the atmosphere concentrated?

stratosphere

Where is most of the water vapour in the atmosphere concentrated?

troposphere

What are the 2 requirements of a mixture of gases for Daltons Law of Partial Pressures to apply to it?

1. the gases must not react

2. the units of P must be the same

how to solve for the mass of a gas using ideal gas law equation

PV = nRT

since n = mass / Molar Mass,

PV = (m / MM) x RT

m / MM = PV / RT

m = PVMM / RT

how to solve for the molar mass of a gas using the ideal gas law equation

PV = nRT

PV = (m / MM) x RT

m / MM = PV / RT

PVMM = PTm

MM = RTm / PV

how to solve for the density of a gas using the ideal gas law equation

PV = nRT

P(m / D) = nRT

m / D = nRT / P

DnRT = mP

D = mP / nRT