A car burning lead-free fuel has a catalytic converter fitted to its exhaust. On analysis its exhaust
gases are shown to contain small quantities of nitrogen oxides.
Which modifications would result in lower exhaust concentrations of nitrogen oxides?
1 an increase in the surface area of the catalyst in the converter
2 an increase in the rate of flow of the exhaust gases through the converter
3 a much higher temperature of combustion in the engine
Answer: 1 only
I understand 1 but not really sure about 2 and 3.
Someone please explain. Thanks!
I believe I will do the trick.
I don't think 2 will work; flowing the gases through the converter faster will result in less time for reaction and that will be a negative effect.
If I looked up the 1/2N2 + 1/2O2 --> NO right ( you should confirm this) it was + meaning endothermic. So raising the engine combustion temperature would make it easier to form NO2 and that would make the converter work harder.
I would go with 1.
let's first understand the question. the question is indirectly asking us how to make the catalytic converter more efficient so that it can catalyse oxides of nitrogen back to nitrogen and oxygen (which are harmless gases as they are present in the atmosphere naturally). statement 1 is correct because when the surface area increases, the rate of reaction also increases and so more oxides of nitrogen are broken down. statement 2 is incorrect because if we increase the rate of flow of the exhaust gases, not enough time is available for the reaction to occur and less oxides of nitrogen are broken down. statement 3 is incorrect as well because if you increase the temperature further, the triple bond between N2 molecules will break as the activation energy is reached and more oxides of nitrogen will be formed. therefore, answer is D/1 only is correct. sorry for the late response lol.
The modification of increasing the rate of flow of the exhaust gases through the converter (option 2) would not result in lower exhaust concentrations of nitrogen oxides. This is because the rate of flow does not directly affect the chemical reactions that occur within the catalytic converter. The surface area of the catalyst plays a more significant role in promoting the reaction that reduces nitrogen oxides.
Similarly, a much higher temperature of combustion in the engine (option 3) would not necessarily result in lower nitrogen oxide concentrations. In fact, higher temperatures can actually lead to increased formation of nitrogen oxides. The catalytic converter is designed to function optimally within a specific temperature range, so excessively high temperatures may hinder its ability to effectively reduce nitrogen oxides.
Therefore, in this case, the only modification that would result in lower exhaust concentrations of nitrogen oxides is an increase in the surface area of the catalyst in the converter (option 1). By increasing the surface area, more catalytic sites are available for the reactions that convert nitrogen oxides into less harmful substances.
Certainly!
To understand the impact of options 2 and 3, let's first discuss the role of a catalytic converter and why nitrogen oxides (NOx) are formed in the exhaust gases.
A catalytic converter is a device in the car's exhaust system that helps to reduce harmful emissions. It contains a catalyst, typically consisting of metals like platinum, palladium, and rhodium, which facilitates the conversion of harmful pollutants into less harmful substances.
Nitrogen oxides (NOx) are formed during the combustion process in the engine. They are primarily caused by the reaction of nitrogen and oxygen in the air at high temperatures. The catalytic converter aims to reduce the concentration of NOx in the exhaust gases by facilitating chemical reactions that convert NOx into harmless nitrogen (N2) and oxygen (O2).
Now let's address options 2 and 3:
2. An increase in the rate of flow of the exhaust gases through the converter.
Increasing the exhaust gas flow rate through the catalytic converter can have a minor effect on reducing NOx emissions. This is because a higher flow rate allows less time for chemical reactions to occur, potentially reducing the conversion of NOx into harmless nitrogen and oxygen. However, the impact of increased flow rate on NOx reduction is typically smaller compared to other factors such as catalyst efficiency. Therefore, in this case, option 2 is not as effective in lowering the concentration of nitrogen oxides.
3. A much higher temperature of combustion in the engine.
Contrary to what might be expected, increasing the temperature of combustion in the engine can actually increase NOx emissions. Higher temperatures during combustion favor the formation of nitrogen oxides. The catalytic converter is designed to work within a specific temperature range for optimal performance. If the combustion temperatures are too high, it can exceed the catalyst's ability to convert NOx effectively. Consequently, a much higher temperature of combustion in the engine, as mentioned in option 3, could lead to higher concentrations of NOx in the exhaust gases.
In summary, for the given question, the modification that would result in lower exhaust concentrations of nitrogen oxides is option 1: an increase in the surface area of the catalyst in the converter. This modification would enhance the efficiency of the catalytic converter in reducing NOx emissions by providing more active sites for the required chemical reactions.