Unit 5 - Gases and Atmospheric Chemistry

Question 1

What is kinetic molecular theory?

Answer 1

the entities in solids, liquids, and gases are in constant, random motion

Question 2

How do entities move?

Answer 2

translational motion, rotational motion, and vibrational motion

Strong attractions between particles limit motion

Question 3

What is kinetic energy?

Answer 3

energy possessed by a moving object

Question 4

What is temperature?

Answer 4

a measure of the average kinetic energy of the entities in a substance

Question 5

What happens when a substance is warmed?

Answer 5

When a substance is warmed, the kinetic energy of its entities increase, resulting in more rapid motion. Eventually, the attractive forces
between particles are broken, allowing them to flow past each
other (i.e., a change of state)

Question 6

What is the earth’s atmosphere?

Answer 6

a thin blanket of moisture and gases that protects us from the hostile environment of outer space (troposphere, stratosphere, mesosphere, thermosphere)

Question 7

Patterns in the earth atmosphere:

Answer 7

• air molecules are pushed together by the atmosphere above them
• As you move further above sea level, air density decreases and consequently, oxygen concentration also decreases
• Air density decreases as altitude increases since there is “less” atmosphere pushing down on the air molecules

Question 8

Atmospheric composition:

Answer 8

• he troposphere and stratosphere have the biggest influence on us due to their proximity
• N2(g) and O2(g) are the most abundant in these layers
• Nitrogen found in proteins and DNA
• Nitrogen-fixing bacteria convert N2(g) into soluble nitrates that
  plants can absorb
• N2(g) is released back into the atmosphere through decaying
  plants and animals and their wastes

Question 9

Oxygen and other gases in the atmosphere:

Answer 9

• Oxygen in the atmosphere is found in the form O2(g) and O3(g) (ozone) –> Ozone acts as a radiation shield by absorbing UV light from the sun, and preventing excessive
• UV radiation from reaching Earth’s surface
• Other gases in the atmosphere include argon, water vapour (99% is in the troposphere), and carbon dioxide
  a) Carbon dioxide is required for photosynthesis
  b) CO2(g) returned through cellular respiration

Question 10

What is the Greenhouse affect?

Answer 10

a natural process whereby gases and clouds absorb infrared (IR) radiation emitted from Earth’s surface and radiate it, heating the atmosphere and Earth’s surface
- When GHG absorb specific frequencies of IR radiation, they vibrate and re-radiate this energy back to Earth where it warms the ground (i.e., IR radiation is trapped within the atmosphere)

Question 11

What are air pollutants?

Answer 11

1. Photochemical smog: is a hazy cloud of gases and air pollutants formed by the reaction of emissions of factories and vehicles with sunlight
2. Particulate matter is the mixture of very small solid and liquid particles found in the atmosphere
   a) Particulate matter can damage the respiratory system when inhaled into the lungs, reduce visibility, and interrupt air travel (e.g., volcanic eruption)

Question 12

What are chemical pollutants?

Answer 12

• Particulate matter can be released indoors from printers, fireplaces, wood-burning stoves, candles, etc.
• Off-gassing: is the release of one or more gases from a substance at room temperature
• Methanal: a VOC, is a colourless, flammable gas often found in preservative and embalming fluid
  a) Commonly found in low amounts in our indoor air from pressed wood products, paints, certain paper products, and fabrics
• Carbon monoxide is a colourless, odourless, tasteless gas (at room temperature) that binds to hemoglobin and blocks it from carrying oxygen to our tissues
  a) CO poisoning: headache, dizziness, weakness, nausea and vomiting, shortness of breath, …

Question 13

What are biological pollutants?

Answer 13

• Dust mites: live in warm, humid environments (e.g., linens, mattresses, pillows, carpets), feed on shed skin
  cells, and their wastes are the most common household allergen
• Mould refers to various species of fungi that grow indoors and their spores can cause respiratory difficulties, skin rashes, or other allergic reactions

Question 14

What are atmospheric pressure?

Answer 14

The force per unit area exerted by air on all objects (SP, STP, SATP)
- As pressure increases, gas density decreases –> closer to the earth
- At higher altitudes, the atmospheric pressure is less than the air in your middle ear
- Volume of air in the middle ear expands and presses the eardrum out

Question 15

Why do your ears pop in high altitude?

Answer 15

due to the different pressure inside the middle ear and the atmosphere

Question 16

What is Charle’s law?

Answer 16

States that the volume of a gas is directly proportional to its temp (in kelvins) if the pressure and amount of gas is constant

Question 17

What is Boyle’s law?

Answer 17

States that the volume of a gas is inversely proportional to its pressure, if the temp and amount of gas are constant

Question 18

What is the Gay-Lussac’s Law?

Answer 18

States that the pressure of a gas is directly proportional to its temp, in Kelvins, if the volume and amount of gas is constant
In molecular theory, if temp increases, kinetic energy increases, with greater kinetic energy, molecules tend to coilide and causes pressure to increase

Question 19

What is the combined gas law used for?

Answer 19

Dealing with calculations involving changes in volume, temp, or pressure for a fixed amount of gas

Question 20

What is the law of combining volume?

Answer 20

When volume of gaseous reactants and products of chemical relations are always in simple ratios of whole numbers (temp and pressure must be constant)

Question 21

What are the pattern’s in avo’s law?

Answer 21

• Since the temperature of both gases is the same, the kinetic energy of both samples is the same
• In order for the pressure (number of collisions) to be equal, the number of particles must be the same
• If the number of entities is the same, then the number of moles is also the same

Question 22

What is avo’s law?

Answer 22

The volume of a gas is directly proportional to the amount (n) of the gas at the constant temp and pressure

Question 23

What is the molar volume?

Answer 23

The volume occupied by one mole of a gas at a specified temp and pressure
- STP: 22.4 L
- SATP:24.8 L

Question 24

What is ideal gas?

Answer 24

All gas laws are based on the assumption that the gas behave “ideally”
Properties:
- They move in straight lines, but in random directions
- No kinetic energy is lost when ideal gases collide (i.e., collisions are perfectly elastic)
- The volume of an ideal gas is insignificant (zero) compared to the volume of the container
- There are no attractive or repulsive forces between gas molecules
- They do not condense to liquids when cooled

Question 25

What is high pressure?

Answer 25

• At high pressure, gas entities experience more collisions, increasing the attraction between entities
• At low volumes as well, the volume of gas entities is significant with the size of the container

Question 26

What is low temperature?

Answer 26

• At low temperature, kinetic energy decreases and real gas entities travel slow
• At reduced speeds, real gas entities can no longer overcome the force of attraction when they collide

Question 27

How to explain Charle’s law?

Answer 27

As temp increase, kinetic energy of the gas particles also increase –> more collusions

Question 28

How to explain Boyle’s law?

Answer 28

As volume decreases, gas particles have less space, causing more collusions, meaning higher pressure

Question 29

What is partial pressure of a gas?

Answer 29

Within a mixture, where gases present have the same volume and temperature

Question 30

What causes partial pressure?

Answer 30

• The pressure of a gas is caused by the collisions of molecules with the walls of the container
• Gas entities act independently of each other
• In a mixture of gases, since the gas particles do not interact with each other (i.e., no intermolecular forces or chemical reactions occur), the total pressure should equal the sum of their individual pressures

Question 31

How do you collect gas over water?

Answer 31

The result causes gas to push the glass and water molecules to leave. Leaving water vapour and other gases.