Chemestry

Question 1

Sulfur dioxide (SO2) concentration in troposphere

Answer 1

0.1-0.5 ppm common urban concentration
Less than 1 ppb far from industri
More than 2 ppm in highly polluted areas

Question 2

Nitrous oxide

Answer 2

dinitrogen oxide N2O
greenhouse gas
unknown effects

Question 3

Nitric oxide

Answer 3

NO

Question 4

Main source of nitrous oxide in atmosphere:

Answer 4

Microbal reduction of nitrate (NO3 -) occurs in soils and waters with low oxygen contents.

Question 5

Nitrous oxide is broken down:

Answer 5

In stratosphere: (2 reactions)

• 2N2O + hv = 2N2 + O2 (sunlight)
• N2O + O* = 2NO (Highly reactive atomic oxygen from ozone reaction, exited)

Question 6

Photodissociation of ozone in Stratosphere:

Answer 6

O3 + hv (lambda - 325nm) = O* + O2

Question 7

Describe CFCs

Answer 7

• Freons used as coolants, propellants and solvents.
• Destroys the ozone layer
• Greenhouse gas
  (- decresing due to Montreal protocol)

Question 8

Describe HFC

Answer 8

• Sustitute to freons/CFCs
• Not bad for ozone
• Also a greenhouse gas

Question 9

What does the Nitrogen molecule in air look like?

Answer 9

N2 - Tripple bond
3 covalent bonds
6 shared electrons
Very strong!

Question 10

pH of seawater?

Answer 10

8-10 (alkaline) becomming more acidic

Question 11

pH rain?

Answer 11

• Unpolluted 5.5 (CO2 makes it naturaly acidic)

- Polluted 4.5 (polluted surface water)

Question 12

What is mole?

Answer 12

• the amount of a substance that contains 6.0225210^23 particles, Avogadros number
  m_a = n_aM_a
• m_a: mass of substance [g]
• n_a: number of mole [mole]
• M_a: molar mass of emelemnt or molecule [g/mol]

Question 13

What is Molarity?

Answer 13

• the concentration of a substance in a certain volume of

another substance very common (like water) [mole/L]

Question 14

How much of the Atmospheric mass is found in the troposphere?

Answer 14

90%

Question 15

What molecules can absorb IR (are GHG):

Answer 15

Only di-pol molecules like:

- H2O, CO2, CH4, NOx, halocarbons etc

Question 16

Photodissociation of ozone in Troposphere:

Answer 16

O3 + hv (lambda < 310nm) -> O* + O2

Question 17

How is methane broken down in troposphere?

Answer 17

O* + CH4 = OH + CH3
OH + CH4 = H2O + CH3
O* from ozone break down

Question 18

How are OH radicals made in troposphere?

Answer 18

• O* + CH4 = OH + CH3
• O* + H2O = 2OH
  O* from ozone break down

Question 19

Why is tropospheric hydroxyl (OH) good?

Answer 19

• It reacts with CO, CH4 and other VOC

cleaning up the atmosphere of pollutants.

Question 20

OH production during day or night?

Answer 20

production of OH is a daytime reaction. Needs the sunlight to break down ozone.

Question 21

Why do we need NO3 when NOx is so harmful?

Answer 21

NO3 is needed in troposphere to remove pollutants in cities during nighttime.
- created from NO2 by removing tropospheric ozone.

Question 22

Where does sulphur pollutants come from?

Answer 22

• Volcanos

- Domestic and industriel combustion of fossil fuel (petroleum and Coal)

Question 23

Where does nitrogen oxides come from?

Answer 23

• Microbial activity in soil and lightning

- High temperature processes (combustion)

Question 24

Where does Volatile Organic Compounds (VOC) come from?

Answer 24

• isoprene rubber, vegitation (non methane)

- Solvents, fuel from petroleum

Question 25

What is London smog?

Answer 25

• H2SO4
• formed during cold winter nights
• from SO2, fog and soot particles.
  (- Deadly in high concentrtions.)

Question 26

What is photochemical (LA) smog?

Answer 26

• Aldehydes, PAN, ozone
• formed sunny days with car traffic
• from NOx, VOC, unburned fuel from cars.

Question 27

What is a free radical?

Answer 27

• And atom, molecule or ion with an unpaired valence electron.
• Highly reactive.

Question 28

What is the problem with NOx and ozone?

Answer 28

They can be part of the rection that produces tropospheric ozone, and they can also act as X and OX in the reaction of ozone destruction in the stratosphere.

Question 29

How is the daily distribution of photochemical smog?

Answer 29

• morning: NO, Hydrocarbons (cars)
• NO2
• lunchtime: ozone, aldehydes (sunlight)

Question 30

End product when nitrogen gets oxidized in atmosphere?

Answer 30

• There is no real end so to say, since the nitrogen cykle is a chain of continous reactions, thanks to the sunlight that keeps reducing the oxidized nitrogen. N2 is a very stable product (no oxidation) but even that is broken down by lightning or bacteria in soil.

Question 31

Terminator for clorine atom reactions?

Answer 31

CH4 + Cl = CH3 + HCl (Hydrocloric acid)

Question 32

End product for Methane in atmosphere?

Answer 32

• It’s a very slow process but one can say that the end product of methane in the atmosphere is:
  CO2

Question 33

Acid rain:

Answer 33

SO4(2-) (aq)

- from HSO3(-)(aq) + H2O … (+ O3) …

Question 34

Formula for Gibbs free constant:

Answer 34

dG = dH - T*dS
G = Gibbs free energy
H = Entalpy (tables)
S = Entropy (tables)

Question 35

dG <> 0 :

Answer 35

dG < 0 -> sontaneuos

dG > 0 -> NOT spontaneous

Question 36

What can prevent spontaneous reactions from occuring?

Answer 36

High activation energy, Ea

Question 37

Leighton’s relationship:

Answer 37

1: NO + O3 = NO2 + O2
2: NO2 + h*ny = NO + O
3: O + O2 + M = O3 + M
Occurs naturally, not net prod of ozone.

Question 38

Main primary pollutants in acid rain:

Answer 38

• NOx and SO2

Question 39

Main secondary pollutants in acid rain:

Answer 39

H2SO4, HNO3
sulphur acid, nitric acid
svavelsyra, salpetersyra