Page 169 - Basic physical chemistry for the atmospheric sciences

Photochemistry

i
(i) Following the large volcanic eruption of Mt. Pinatuho n
the Philippines i n 1 9 9 1 , which injected large quantities
of sulfur dioxide into the stratosphere, temporary depic­
tions in stratospheric ozone of 5-8% were observed
above the tropic .
s
(j) For catalytic cycles such s Reactions (7.28) o b e effi­
a
t
cient, each reaction comprising the cycle must be exo­
thermic .
7 . 7 . Compare the magnitude of the energy of an einstein of U V
radiation (take A = 0. 1 µm) with the energies of a weak
chemical bond (say I eV), a strong chemical bond (say 1 0
V
e ) , and the kinetic energy of impact f two molecules (say
o
0.05 eV).
o
7 . 8 . The shortest wavelength f solar radiation that reaches the
lower atmosphere is about . 3 µm. What is the energy asso­
0
ciated with I einstein of this radiation?
7 . 9 . The ionization energies fo r nitrogen (N 2) and oxygen (02)
, respectively . What are the
are 1 , 495 and 1 , 205 kJ mole - 1
maximum wavelengths of solar radiation that can ionize
nitrogen and oxygen? Where do these wavelengths lie in the
em spectrum?
7 1 0. How many photons , with the required minimum energy , are
.
required to produce 1 . 0 kg of OH in the following pho­
tolytic reaction?
H20(g) + v ----'> OH(g) + H(g)
h
Assume that each photon is absorbed by a water molecule
which then photolyses. The bonding energy of the 0---H
bond in H20 is 5 . 2 eV .
7 . 1 1 . If eight photons of red light of wavelength 0 . 6 85 µm are
needed to produce one molecule of oxygen, and if the aver­
age energy stored in the photosynthetic process is 470 kJ per
mole of oxygen, what is the energy conversion efficiency of
photosynthesis with respect to oxygen?
7 . 1 2 . The concentration of ozone just above the Earth's surface
is . 0 40 ppmv, and the rate coefficients for the reactions
0
NOz(g) + v ----'> NO(g) + O(g)
h
and,