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Environmental scientists continue to be concerned about the slow recovery of ozone concentrations in the stratosphere despite the successes of the 1987 Montreal Protocol, an international treaty designed to control substances that deplete ozone - Leaving Cert Chemistry - Question A - 2016
Question A
Environmental scientists continue to be concerned about the slow recovery of ozone concentrations in the stratosphere despite the successes of the 1987 Montreal Prot... show full transcript
Worked Solution & Example Answer:Environmental scientists continue to be concerned about the slow recovery of ozone concentrations in the stratosphere despite the successes of the 1987 Montreal Protocol, an international treaty designed to control substances that deplete ozone - Leaving Cert Chemistry - Question A - 2016
Step 1
What is the beneficial effect of the ozone layer?
Answer
The ozone layer serves a critical role in protecting life on Earth. It absorbs the majority of the Sun's harmful ultraviolet (UV) radiation. This absorption not only protects human health by reducing the risk of skin cancer and cataracts but also safeguards ecosystems and wildlife. Additionally, the ozone layer plays a vital role in regulating temperatures in the Earth's atmosphere, contributing to climate stability.
Step 2
How is ozone formed in the stratosphere?
Answer
Ozone is formed in the stratosphere through a photochemical reaction involving oxygen molecules. When UV radiation from the Sun strikes oxygen molecules (O₂), it breaks them apart into individual oxygen atoms (O). These reactive oxygen atoms can then react with unbroken O₂ to form ozone (O₃). The reaction can be summarized by the following equations:
- Photodissociation of oxygen:
ightarrow 2 ext{O}$$
- Formation of ozone:
ightarrow ext{O}_3$$
Step 3
Describe using balanced equations why chlorine radicals are so damaging to the ozone layer.
Answer
Chlorine radicals, released from chlorofluorocarbons (CFCs), are highly reactive and can destroy ozone molecules. The process can be described in the following steps:
- A chlorine radical reacts with an ozone molecule:
ightarrow ext{ClO} + ext{O}_2$$
- The chlorine monoxide can further react with another ozone molecule or with another free radical:
ightarrow ext{Cl} + ext{O}_2$$
This cycle can continue, where one chlorine radical can destroy thousands of ozone molecules before being removed from the atmosphere.
Step 4
Why are HCFCs significantly less damaging to the ozone layer than CFCs?
Answer
HCFCs (hydrochlorofluorocarbons) are significantly less harmful to the ozone layer compared to CFCs due to their chemical structure. HCFCs break down more readily in the lower atmosphere and do not reach the stratosphere as effectively as CFCs. As a result, they release fewer chlorine radicals at altitudes where ozone depletion occurs. Furthermore, HCFCs have a shorter atmospheric lifetime, making them less reactive and less damaging to the ozone layer.