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Biology; Chemistry; Physics: Post your doubts here!

Saad Mughal

Saad Mughal

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kashaf shahzad said:
And if somebody could explain where does the equilibrium shifts in a chemical reaction which is in equilibrium and when one of the three facters (pressure,temperature and moles)are changed.And with reasoning.This is a topic from chemistry o levels Gce.
Click to expand...
Le Chatelier's Principle states that if a change is brought about to a body in dynamic equilibrium, the body acts to oppose the change. Now, this can be applied to the following factors:
- Pressure: Increasing the pressure decreases the volume, which means that body will work to oppose the change and increase the volume again. It does this by breaking or making bonds; now, if, for example ammonia is considered, N2 + 3H2 <----> 2NH3, since the number of molecules on the left is HIGHER than on the right, the body makes more molecules to increase the volume. This increases the yield of ammonia.
- Temperature: Increasing the temperature means providing more heat to the body, the body works to oppose this change by absorbing heat, this means that the ENDOTHERMIC part of the reaction is favored. For production of Ammonia, the forward reaction (N2 + 3H2 ---> 2NH3) is exothermic which means that increasing the temperature would actually decrease the yield because the body would favor the backward reaction which is ENDOTHERMIC.
- Moles: This has no effect whatsoever because the % yield in any case remains the same, if say, 100g of N2 and H2 produce 50g of NH3, then increasing the moles to 200g of N2 and H2 would produce 100g of NH3, which is useless because the priority is to increase the yield.
- Catalyst: The catalyst has no effect on the yield but it does speed up the reaction to a great extent (which means that equilibrium is reached quickly) and since 'time is money in industry' then increasing the speed does matter.
Hope that helps! :)
 
K

kashaf shahzad

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Saad Mughal said:
Le Chatelier's Principle states that if a change is brought about to a body in dynamic equilibrium, the body acts to oppose the change. Now, this can be applied to the following factors:
- Pressure: Increasing the pressure decreases the volume, which means that body will work to oppose the change and increase the volume again. It does this by breaking or making bonds; now, if, for example ammonia is considered, N2 + 3H2 <----> 2NH3, since the number of molecules on the left is HIGHER than on the right, the body makes more molecules to increase the volume. This increases the yield of ammonia.
- Temperature: Increasing the temperature means providing more heat to the body, the body works to oppose this change by absorbing heat, this means that the ENDOTHERMIC part of the reaction is favored. For production of Ammonia, the forward reaction (N2 + 3H2 ---> 2NH3) is exothermic which means that increasing the temperature would actually decrease the yield because the body would favor the backward reaction which is ENDOTHERMIC.
- Moles: This has no effect whatsoever because the % yield in any case remains the same, if say, 100g of N2 and H2 produce 50g of NH3, then increasing the moles to 200g of N2 and H2 would produce 100g of NH3, which is useless because the priority is to increase the yield.
- Catalyst: The catalyst has no effect on the yield but it does speed up the reaction to a great extent (which means that equilibrium is reached quickly) and since 'time is money in industry' then increasing the speed does matter.
Hope that helps! :)
Click to expand...
Tha
Saad Mughal said:
Le Chatelier's Principle states that if a change is brought about to a body in dynamic equilibrium, the body acts to oppose the change. Now, this can be applied to the following factors:
- Pressure: Increasing the pressure decreases the volume, which means that body will work to oppose the change and increase the volume again. It does this by breaking or making bonds; now, if, for example ammonia is considered, N2 + 3H2 <----> 2NH3, since the number of molecules on the left is HIGHER than on the right, the body makes more molecules to increase the volume. This increases the yield of ammonia.
- Temperature: Increasing the temperature means providing more heat to the body, the body works to oppose this change by absorbing heat, this means that the ENDOTHERMIC part of the reaction is favored. For production of Ammonia, the forward reaction (N2 + 3H2 ---> 2NH3) is exothermic which means that increasing the temperature would actually decrease the yield because the body would favor the backward reaction which is ENDOTHERMIC.
- Moles: This has no effect whatsoever because the % yield in any case remains the same, if say, 100g of N2 and H2 produce 50g of NH3, then increasing the moles to 200g of N2 and H2 would produce 100g of NH3, which is useless because the priority is to increase the yield.
- Catalyst: The catalyst has no effect on the yield but it does speed up the reaction to a great extent (which means that equilibrium is reached quickly) and since 'time is money in industry' then increasing the speed does matter.
Hope that helps! :)
Click to expand...
It was of great help.Thank you.
 
Saad Mughal

Saad Mughal

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Zoya Shahab said:
It has total 7 electrons. 2 in first shell... 8 in every shell onward...53-2=51...51/8=6 3/8
so wont it have 3 electrons in last shell???
Click to expand...
After calcium, the structure isn't that simple.
The structure is like, 2,8,8,2 then the third shell fills again, it becomes 2,8,18,2 and then the fourth shell is completed and so on. Its pretty complex and not part of the syllabus. That is why you should ALWAYS consider the GROUP NUMBER to draw the structure.
 
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