O3

Question 1

What is the function of the O3 layer?

Answer 1

The absorption of UV rays.

Question 2

What have been the consequences of pollution?

Answer 2

A large hole over Antarctica, appearing over it every spring, largest in 2006.

Question 3

What is the stratosphere?

Answer 3

Region lying between altitudes where temperature trends reverse, the bottom where it stops decreasing with height and begins to increase.

Question 4

What are the two concentration measurements used to discuss gases within the atmosphere?

Answer 4

Absoloute and relative.

Question 5

What is absolute concentration?

Answer 5

Number of molecules per cubic centimeter of air, or expressed as partial pressure.

Question 6

What is the Ideal Gas Law?

Answer 6

This states that partial pressure id proportional to molar concentration, and thus molecular concentration per unit volume.

Question 7

What is relative concentration?

Answer 7

This measures parts per x value, like amount of CO2 per 1 million molecules of air.

Question 8

Why is relative concentration used?

Answer 8

Where concentrations are so small.

Question 9

What is the absorption spectrum?

Answer 9

This graphically represents relative fraction of light absorbed by a molecule, as a function of wavelength.

Question 10

What roles does O2 play in the atmosphere?

Answer 10

Filters UV light between 120-220nm above the stratosphere, and shorter than 120nm.

Question 11

What filters UV from 220-290nm?

Answer 11

O3.

Question 12

What UV does O3 not absorb?

Answer 12

290-320nm, thus 10-30%(depending on latitude), hits earth surface, this being UV-B.

Question 13

What does E= hv describe?

Answer 13

Energy is related to frequency and the wavelength.

Question 14

What does this imply?

Answer 14

That the lower the energy, the greater the wavelength.

Question 15

How does photon energy relate to enthalpy change?

Answer 15

Proportional

Question 16

What is an applied example?

Answer 16

O2 disassociation into 2 O requires 498.4 kJ/mol enthalpy change

Question 17

How much energy thus is required to dissassociate?

Answer 17

240nm, this being the enthalpy of a single O.

Question 18

What type of reaction is this?

Answer 18

Photochemical reaction.

Question 19

What happens to a compound in an excited state?

Answer 19

Immediate return to ground states by photon emission or heat transfer to free atoms/molecules through collisions.

Question 20

What does this mean for photolytic initiation?

Answer 20

Inability to accumulate energy from several photons, thus wavelengths higher than 240nm cannot disassociate.

Question 21

Why does most oxygen exist atomically above the stratosphere?

Answer 21

UV-C disassociation of O2, with reformation by collision into O2, however very thin.

Question 22

Why is atomic O more likely to react with O2 in the stratosphere?

Answer 22

Because O2 concentration is so large and O concentration is so small, thus forming ozone.

Question 23

Why is little ozone formed at the bottom of the stratosphere?

Answer 23

Less O due to less O2 dissociation and more O2 as air density increases approaching the surface.

Question 24

Where does O3 concentration maxmise?

Answer 24

Where UVC intensity and O2 is greatest

Question 25

Why is the temperature above/below the stratosphere lower?

Answer 25

Heat generated by O + O2 collision.

Question 26

How does UV-C and UV-B react with ozone?

Answer 26

Efficient absorption and dissociation into O2 and O, which subsequently reform O3, or O destroys O3 through reacting to two O2.

Question 27

What is the Chapman Cycle?

Answer 27

This is the process of continous regeneration of O3 in the stratosphere.

Question 28

Why is the term ‘ozone layer’ a misnomer?

Answer 28

The majority of it is NOT O3.

Question 29

How can pollutants then act as catalysts for O3 destruction?

Answer 29

Form a compound with O, and O2, then the pollutant-O xompound reacts with O, producing O2 and the standalone compound, further destroying O3.

Question 30

Where does this specific type of reaction occur?

Answer 30

Middle and upper stratosphere by free radicals.

Question 31

What is an example of a natural catalytic O3 pollutant?

Answer 31

Ntiric oxide, produced when N2O rise from troposphere to stratosphere.