Which one of the following statements with regard to ozone is NOT correct?
16th November is celebrated as the International Day for the Preservation of the Ozone Layer.
Understanding Ozone and the Atmosphere
The question asks us to identify the statement that is NOT correct regarding ozone. Ozone (\(\text{O}_3\)) is a molecule made up of three oxygen atoms. It plays a crucial role in Earth's atmosphere, particularly in absorbing harmful ultraviolet (UV) radiation from the sun.
Composition and Formation of Ozone
Ozone is indeed a form of oxygen, but instead of the common two-atom molecule (\(\text{O}_2\)), it has three oxygen atoms bonded together. This fits statement 4.
Ozone is primarily formed in the atmosphere through chemical reactions involving oxygen molecules and sunlight. This process typically starts with ultraviolet radiation breaking apart an oxygen molecule (\(\text{O}_2\)) into two individual oxygen atoms (\(\text{O}\)). These single oxygen atoms then combine with other oxygen molecules (\(\text{O}_2\)) to form ozone (\(\text{O}_3\)). This is a type of gaseous chemical reaction, which supports statement 2.
The overall reactions can be summarized as:
- \(\text{O}_2 + \text{UV} \rightarrow \text{O} + \text{O}\)
- \(\text{O} + \text{O}_2 \rightarrow \text{O}_3\)
Location of Ozone in the Atmosphere
Ozone is present throughout the atmosphere, but its concentration is highest in the stratosphere, which is the layer above the troposphere (where we live). This region of high ozone concentration is known as the ozone layer. The stratosphere extends from about 10 km to 50 km above the Earth's surface. Statement 1 suggests ozone is mostly found at 15-55 km, which is consistent with the location of the ozone layer within the stratosphere.
International Day for the Preservation of the Ozone Layer
To raise awareness about the importance of the ozone layer and the need to protect it, the United Nations designated a specific day as the International Day for the Preservation of the Ozone Layer. This day commemorates the signing of the Montreal Protocol on Substances that Deplete the Ozone Layer. It is widely celebrated globally.
Let's check the date mentioned in statement 3: 16th November. Is this the correct date for the International Day for the Preservation of the Ozone Layer? No, it is not. The actual date for the International Day for the Preservation of the Ozone Layer is 16th September.
Analyzing the Statements
Based on our understanding, let's review each statement:
- Statement 1: Ozone is found mostly at 15-55 km in the atmosphere. This range falls within the stratosphere where the ozone layer is located. This statement is generally considered correct.
- Statement 2: Ozone is produced by gaseous chemical reactions. As explained by the process involving UV radiation and oxygen molecules, ozone formation is indeed a result of gaseous chemical reactions. This statement is correct.
- Statement 3: 16th November is celebrated as the International Day for the Preservation of the Ozone Layer. This statement is incorrect. The correct date is 16th September.
- Statement 4: Ozone is a form of oxygen in which three oxygen atoms are bounded together. The chemical formula for ozone is \(\text{O}_3\), meaning it consists of three oxygen atoms. This statement is correct.
The statement that is NOT correct is the one about the date of the International Day for the Preservation of the Ozone Layer.
| Statement | Assessment | Explanation |
|---|---|---|
| Ozone is found mostly at 15-55 km | Correct | This range is within the stratosphere (ozone layer). |
| Ozone is produced by gaseous chemical reactions | Correct | Formed from \(\text{O}_2\) and \(\text{O}\) under UV light. |
| 16th November is Ozone Day | Incorrect | The correct date is 16th September. |
| Ozone has three oxygen atoms | Correct | Ozone is \(\text{O}_3\). |
Conclusion on Ozone Statements
Comparing all the statements, the one that is factually incorrect is the date given for the International Day for the Preservation of the Ozone Layer. The correct date is 16th September, not 16th November.
Revision Table: Key Ozone Facts
| Aspect of Ozone | Key Information |
|---|---|
| Chemical Formula | \(\text{O}_3\) (Three oxygen atoms) |
| Primary Location | Stratosphere (Ozone Layer, ~15-55 km) |
| Formation Process | Photochemical reactions involving \(\text{O}_2\) and UV light |
| Importance | Absorbs harmful UV-B and UV-C radiation |
| International Day | 16th September |
Additional Information on Ozone and Ozone Layer Preservation
The ozone layer is vital for life on Earth because it prevents most of the sun's harmful UV radiation from reaching the surface. Increased UV radiation can cause skin cancer, cataracts, and harm to ecosystems.
In the 20th century, certain man-made chemicals, particularly chlorofluorocarbons (CFCs) and halons, were found to be depleting the ozone layer. These substances were commonly used in refrigerants, aerosols, and fire extinguishers.
The discovery of the Antarctic ozone hole in the 1980s highlighted the severity of ozone depletion. In response, the international community adopted the Montreal Protocol in 1987, an agreement to phase out the production and consumption of ozone-depleting substances. This protocol is considered a highly successful international environmental treaty, and the ozone layer is projected to recover gradually over the coming decades thanks to these efforts.
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