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Flashcards in Chemestry Deck (39)
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1
Q

Sulfur dioxide (SO2) concentration in troposphere

A

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

2
Q

Nitrous oxide

A

dinitrogen oxide N2O
greenhouse gas
unknown effects

3
Q

Nitric oxide

A

NO

4
Q

Main source of nitrous oxide in atmosphere:

A

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

5
Q

Nitrous oxide is broken down:

A

In stratosphere: (2 reactions)

  • 2N2O + hv = 2N2 + O2 (sunlight)
  • N2O + O* = 2NO (Highly reactive atomic oxygen from ozone reaction, exited)
6
Q

Photodissociation of ozone in Stratosphere:

A

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

7
Q

Describe CFCs

A
  • Freons used as coolants, propellants and solvents.
  • Destroys the ozone layer
  • Greenhouse gas
    (- decresing due to Montreal protocol)
8
Q

Describe HFC

A
  • Sustitute to freons/CFCs
  • Not bad for ozone
  • Also a greenhouse gas
9
Q

What does the Nitrogen molecule in air look like?

A

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

10
Q

pH of seawater?

A

8-10 (alkaline) becomming more acidic

11
Q

pH rain?

A
  • Unpolluted 5.5 (CO2 makes it naturaly acidic)

- Polluted 4.5 (polluted surface water)

12
Q

What is mole?

A
  • the amount of a substance that contains 6.0225210^23 particles, Avogadros number
    m_a = n_a
    M_a
  • m_a: mass of substance [g]
  • n_a: number of mole [mole]
  • M_a: molar mass of emelemnt or molecule [g/mol]
13
Q

What is Molarity?

A
  • the concentration of a substance in a certain volume of

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

14
Q

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

A

90%

15
Q

What molecules can absorb IR (are GHG):

A

Only di-pol molecules like:

- H2O, CO2, CH4, NOx, halocarbons etc

16
Q

Photodissociation of ozone in Troposphere:

A

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

17
Q

How is methane broken down in troposphere?

A

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

18
Q

How are OH radicals made in troposphere?

A
  • O* + CH4 = OH + CH3
  • O* + H2O = 2OH
    O* from ozone break down
19
Q

Why is tropospheric hydroxyl (OH) good?

A
  • It reacts with CO, CH4 and other VOC

cleaning up the atmosphere of pollutants.

20
Q

OH production during day or night?

A

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

21
Q

Why do we need NO3 when NOx is so harmful?

A

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

22
Q

Where does sulphur pollutants come from?

A
  • Volcanos

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

23
Q

Where does nitrogen oxides come from?

A
  • Microbial activity in soil and lightning

- High temperature processes (combustion)

24
Q

Where does Volatile Organic Compounds (VOC) come from?

A
  • isoprene rubber, vegitation (non methane)

- Solvents, fuel from petroleum

25
Q

What is London smog?

A
  • H2SO4
  • formed during cold winter nights
  • from SO2, fog and soot particles.
    (- Deadly in high concentrtions.)
26
Q

What is photochemical (LA) smog?

A
  • Aldehydes, PAN, ozone
  • formed sunny days with car traffic
  • from NOx, VOC, unburned fuel from cars.
27
Q

What is a free radical?

A
  • And atom, molecule or ion with an unpaired valence electron.
  • Highly reactive.
28
Q

What is the problem with NOx and ozone?

A

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.

29
Q

How is the daily distribution of photochemical smog?

A
  • morning: NO, Hydrocarbons (cars)
  • NO2
  • lunchtime: ozone, aldehydes (sunlight)
30
Q

End product when nitrogen gets oxidized in atmosphere?

A
  • 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.
31
Q

Terminator for clorine atom reactions?

A

CH4 + Cl = CH3 + HCl (Hydrocloric acid)

32
Q

End product for Methane in atmosphere?

A
  • It’s a very slow process but one can say that the end product of methane in the atmosphere is:
    CO2
33
Q

Acid rain:

A

SO4(2-) (aq)

- from HSO3(-)(aq) + H2O … (+ O3) …

34
Q

Formula for Gibbs free constant:

A
dG = dH - T*dS
G = Gibbs free energy
H = Entalpy (tables)
S = Entropy (tables)
35
Q

dG <> 0 :

A

dG < 0 -> sontaneuos

dG > 0 -> NOT spontaneous

36
Q

What can prevent spontaneous reactions from occuring?

A

High activation energy, Ea

37
Q

Leighton’s relationship:

A

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

38
Q

Main primary pollutants in acid rain:

A
  • NOx and SO2
39
Q

Main secondary pollutants in acid rain:

A

H2SO4, HNO3
sulphur acid, nitric acid
svavelsyra, salpetersyra