Block 13: Atmospheric Chemistry

Question 1

How does nitric acid formation vary diurnally?

Answer 1

Daytime: NO2 from chimneys interacts with OH radicals (from sun) to create nitric acid
Nighttime: NO2 reacts with ozone to create nitric acid at a slower rate

Question 2

What are the 3 main atmospheric acids & are they primary or secondary pollutants?

Answer 2

HCl: primary
HNO3: secondary
H2SO4: secondary

Question 3

What are the 3 steps of sulphuric acid formation?

Answer 3

SO2 + OH* = HOSO2*
HOSO2* + O2 = HO2* + SO3
SO3 + H2O = H2SO4

Question 4

What do E & B rank in petrol & diesel respectively?

Answer 4

E: plant ethanol in petrol
B: biofuel in diesel

Question 5

When do the worst NOx & CO emissions occur for petrol cars?

Answer 5

NOx: worse on short journeys
CO: worse at the start of short journeys with cold engines

Question 6

What do catalytic convertors do for petrol cars?

Answer 6

Reduce emissions through oxidation of CO & HC into CO2 & H2O as well as reduction of NOx into N2 & O2

Question 7

What do diesel particulate filters & AdBlue do for diesel cars?

Answer 7

Particulate filters trap soot from exhaust
AdBlue is a urea additive that reduces NOx into N2 & H2O

Question 8

What determines the relative ratio of NO to NO2?

Answer 8

The availability of oxidants, as NO becomes NO2 in the presence of O3