All posts by #OOI KEAN HEAN#

BS Batch 2014 LIVE created on 30/04/2014
explaination

Effects of CFC on Ozone Layer

HI!! I would like to bring to your attention how your air conditioners are stabbing you on the back with the CFCs produced.

Giving you a rough idea before going into the details, CFC catalyses the decomposition of Ozone to diatomic Oxygen. Hence, the amount of Ozone decreases.

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CFCs, are molecules in which all four atoms attached to one central carbon are Chlorines and Fluorines. The catalytic properties is due to the Chlorine atom present in the one carbon molecule. When “activated”, CFCs exerts their sinister reactions.

CFCs can be activated by UV light. When shined with UV, which the stratosphere has high exposure to, CFCs undergo a reaction to produce a Chlorine Radical, an atom with an unpaired electron.

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This is known as the Initiation Step, which is UV-induced.

Then, the chlorine radical acts as the catalyst for the destruction of Ozone. As the radical acts as a catalyst, the radical is not consumed  and is able to catalyse more ozone destruction reactions.

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This is known as the Propagation Step, which can go on and on untill several millions of ozone molecules are destroyed. However, two chlorine radicals can react to terminate this propagation, hence, known as the Termination Step.

Hence the overall reaction is depicted as follow.

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To summarise, the chlorine radical provides an alternative pathway for the degradation of Ozone. If uncatalysed, the conversion of ozone molecules to diatomic molecules requires a high input of energy (activation energy) which makes the reaction very very very slow. Below shows the two step pathway that the chlorine radical provides to reduce the energy required to kick start the reaction.

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Hope you enjoyed. Thanks 🙂

References:

H. S. Rzepa (2015) ‘On the overall reaction of Ozone decomposition catalysed by chlorine radical’ Retrieved on 24 March, 2015 from  http://www.ch.ic.ac.uk/rzepa/mim/environmental/html/cfc.htm

Lee Soo Ying (n.d.) CM1041 Kinetics Notes ‘On the catalysed and uncatalysed reaction energy diagram’ Retrieved on 24 March, 2015

 

assignment

Group Discussion on UNIT 3 topics.

1. Understanding Earth’s Energy balance is essential to understading the issue of global warming. For example, the solar energy striking Earth’s surface averages 168 watts per square meter (W/m2), but the energy leaving Earth’s surface averages 390(W/m2). Why isn’t earth cooling rapidly?

After our group discussion, we think that the reason behind this is because our earth’s core is also emitting heat itself. Moreover, there are still heat trapped within the atmosphere which is then later reflected back to Earth. Therefore, when the reflected heat comes back by green house gasses, the atmosphere becomes hotter than before instead of cooling down.

2. Do you think the statement made by the cartoon is justified? Explain.

No, it is definitely not true . First we need to know that the seasons we are experiencing are a result of the Earth’s tilted axis as it revolves around the sun so it doesn’t mean that during winter we can be less concern about global warming  instead the effects of global warming actually become more visible. for example the temperatures during winter.  Numbers have shown that over the past decades, the temperature during winter has significantly increase and this can be due to the effects of global warming as global warming is changing the weather patterns. Avery good example would be Lake Erie not freezing during the winter of 2006 for the very first time in history. This shows that global warming has resulted in warmer temperatures.

Even though there will be variation in the temperature, the overall trend of increasing temperature still exists. This means that the cold weather still occurs, but with an steady rise in temperature in the long run.

3. One of the first radar devices developed during the World War 2 used microwave radiation of a specific wave range that triggers the rotation of water molecules. Why was the design not successful?

This is due to the reason that Water molecule itself is a greenhouse gas. The water molecules present in the atmosphere will absorb the radiation. The radar device is hence ineffective.

The absorption of electromagnetic radiation by water actually depends on the state of the water.

The absorption in the gas phase occurs in three regions of the spectrum. Rotational transitions are responsible for absorption in the microwave and far-infrared, vibrational transitions in the mid-infrared and near-infrared. Electronic transitions occur in the vacuum ultraviolet regions.

Liquid water has no rotational spectrum but does absorb in the microwave region.

Given that water molecules absorbs the microwave radiation, it would be more effective if a higher energy radiation is used. e.g uv but it would in turn lead to undesirable environmental as well as health concerns.

4. Now that you have studied air quality( unit 1), stratospheric ozone depletion(unit2), and global warming( unit 3), which do you believe poses the most serious problem for you in the short run? in the long run?

Air Quality would poses serious problem in short run as it can cause poor health. The effects can be seen almost immediate as air can be measured and categorized. For example, the haze problem in Singapore that happened in 2013 is a very good example of the importance of air quality. When the PSI hit above 400 which is in  the hazardous zone, everyone’s health is put a stake. The picture below shows the seriousness of how air quality is vital. Hence, actions and management can be taken quickly.

After studying the three chapters, it is rather clear that global warming would poses serious problem in long run as the effects are not immediate as the impact is gradually increasing over the years. Some impacts from global warming can already be seen and that includes ice are melting worldwide at a faster rate and sea levels are gradually increasing. Effects that could happen in the century would probably be stronger hurricanes and storms and higher frequency of floods and drought.

As such, it can be seen that this problem of global warming has to solve as soon as possible as by delaying it will only result in increasing the cost of solving the problem in future.  We need to learn how to solve the problem together as a whole otherwise the consequences would be disastrous.