35 Questions
What type of reactions are much slower in the atmosphere?
Endothermic reactions
What is the activation energy required for the reaction to be slow at stratospheric temperatures?
At least equal to 69 kJ mol^-1
What is the energy change (ΔH) for the reaction OH + HF -> H2O + F?
ΔH > 0
What is the energy difference for O* compared to ground-state atomic oxygen?
190 kJ mol^-1
What is the energy difference for the abstraction from water of a hydrogen atom by ground-state atomic oxygen?
69 kJ mol^-1
What type of reaction is the reaction of O* with H2O to give the same products?
Exothermic
What is the ozone layer and why is it important?
The ozone layer is a region of the atmosphere that filters out harmful ultraviolet (UV) rays from sunlight. It is important because it protects humans and other life forms from UV radiation.
What environmental crisis occurred in the mid-1980s related to the ozone layer?
A large 'hole' in the ozone layer over Antarctica appeared, representing a major environmental crisis.
Why is the ozone hole a threat to life on Earth?
Any substantial reduction in the amount of ozone would threaten life as we know it by allowing harmful UV rays to reach the surface and cause damage.
When does the ozone hole over Antarctica typically appear?
The ozone hole over Antarctica typically appears each spring.
What is the significance of the large hole that occurred in the ozone layer in 2006?
One of the largest holes in history occurred in 2006, highlighting the ongoing environmental challenge.
Why is it important to understand the natural chemistry of the ozone layer?
Understanding the natural chemistry of the ozone layer is important to comprehend the processes at work in the ozone hole and the evolution of the hole.
What role do NO molecules play in the destruction of ozone?
Extracting an oxygen atom from ozone and forming nitrogen dioxide
What is the overall reaction involved in the destruction of ozone by NO molecules?
O3 -> 2 O2
What is the rate law for the gas-phase reaction between nitric oxide and ozone?
rate = k [NO] [O3]
What is the value of the rate constant, k, for the reaction between nitric oxide and ozone at an atmospheric temperature of about 50°C?
6.5 x 10^-15 molecules^-1 cm3 sec^-1
How do NO molecules contribute to the formation of nitrogen dioxide in the reaction with ozone?
By extracting an oxygen atom from ozone
Explain the significance of the reaction between nitric oxide and ozone in terms of atmospheric chemistry.
This reaction contributes to the destruction of ozone, impacting the ozone layer and atmospheric composition.
What is the overall reaction of Mechanism II involving ozone molecules?
2 O3 --> 3 O2
What is the significance of a species shown in square brackets in chemistry?
It indicates a species with a transient existence.
What must either X or X be in Mechanism II?
A chlorine atom
What happens to the catalysts X and X in Mechanism II after the reaction steps?
They are ultimately regenerated
What is the role of UV light in the production and destruction of ozone?
UV light is essential for the production of ozone from oxygen
What is the main cause of ozone loss in the lower stratosphere?
Mechanism II
What are the three gases that constitute most of the Earth's atmosphere?
Nitrogen, Oxygen, Argon
What is the range of altitudes that constitutes the troposphere?
0-12 km
What is the range of altitudes that constitutes the stratosphere?
12-50 km
What is the primary atmospheric gas responsible for filtering sunlight in the 120-220 nm region?
Ozone
What is the wavelength range for visible light? Does ultraviolet light have shorter or longer wavelengths than visible light?
Visible light ranges from 400-700 nm. Ultraviolet light has shorter wavelengths than visible light.
Write the equation for the chemical reaction by which ozone is formed in the stratosphere. What are the sources for the different forms of oxygen used as reactants?
O2 + O -> O3; Molecular oxygen (O2) and atomic oxygen (O) are the sources for the reactants.
What are the equations relating photon energy E to light's frequency ν and wavelength λ?
E = hν = hc/λ
What are the two reactions that contribute most significantly to ozone destruction in the stratosphere, aside from catalyzed reactions?
O3 + O -> 2O2; O3 + UV light -> O2 + O
What is meant by the term 'excited state' as applied to an atom or molecule? How is an excited state symbolized?
An 'excited state' is a state in which an atom or molecule has absorbed energy and moved to a higher energy level. It is symbolized by an asterisk (*) next to the chemical symbol.
Explain why the phrase 'ozone layer' is a misnomer.
The ozone layer is not a distinct layer but a region with varying concentrations of ozone. It is not a separate, well-defined layer.
Define the term 'free radical' and provide two examples relevant to stratospheric chemistry.
A free radical is a highly reactive species with an unpaired electron. Examples in stratospheric chemistry include hydroxyl radical (OH•) and nitric oxide (NO).
Explore introductory chemistry topics related to the ozone layer, including moles, ideal gas law, thermochemistry, and kinetics. Learn how the ozone layer acts as Earth's natural sunscreen by filtering out harmful UV rays from sunlight.
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