Author Topic: Chemistry Equilibrium Reaction Help ASAP Please!  (Read 5093 times)

Offline skylite

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Chemistry Equilibrium Reaction Help ASAP Please!
« on: May 05, 2013, 07:00:16 am »
Hi guys I'm new here and taking the O levels 2013 soon. :)

Here's my question: For this reaction
N2 (g) + 3H2 (g) -> 2NH3 (g)  (reaction exothermic)

What will happen to the yield when the Temperature is increased/decreased?
and What will happen to the yield when the Pressure is increased/decreased?

Can anyone please explain? Thanks ;D
« Last Edit: May 07, 2013, 01:59:53 pm by NotAbod »

Offline NotAbod

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Re: Chemistry Equilibrium Reaction Help ASAP Please!
« Reply #1 on: May 05, 2013, 09:28:14 am »
Increasing temperature will shift equilibrium to the endothermic side of the reaction (ie forward reaction). Product yield will increase.
Decreasing temperature will shift equilibrium to the exothermic side of the rection (ie left side). Product yield will decrease.


Increasing pressure will shift equilibrium to the side having less number of moles (reactants = 4 moles, products = 2 moles). Product yield will increase.
Decreasing pressure will shift equilibrium to the side having more moles (left side). Product yield decreases.
« Last Edit: May 07, 2013, 02:01:24 pm by NotAbod »

Offline Deadly_king

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Re: Chemistry Equilibrium Reaction Help ASAP Please!
« Reply #2 on: May 05, 2013, 03:52:35 pm »
Hi guys I'm new here and taking the O levels 2013 soon. :)

Here's my question: For this reaction
N2 (g) + 3H2 (g) -> 2NH3 (g)  (reaction exothermic)

What will happen to the yield when the Temperature is increased/decreased?
and What will happen to the yield when the Pressure is increased/decreased?

Can anyone please explain? Thanks ;D

The basic rule here is to understand Le Chatelier's Principle ;)

Understand the rule properly and you'll have no problem in any questions concerning equilibria ;)

Offline skylite

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Re: Chemistry Equilibrium Reaction Help ASAP Please!
« Reply #3 on: May 07, 2013, 01:55:46 pm »
Thanks for your attention but I'm still quite confused about this :s

Increasing temperature will shift equilibrium to the endothermic side of the reaction (ie forward reaction). Product yield will increase.
Decreasing temperature will shift equilibrium to the exothermic side of the rection (ie left side). Product yield will decrease.

My friend said that the yield will actually decrease when the temperature is increased. So the reaction will favour the right side which produces more ammonia. Is my friend wrong?

Chem is too complicated x_x

Offline NotAbod

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Re: Chemistry Equilibrium Reaction Help ASAP Please!
« Reply #4 on: May 07, 2013, 02:00:41 pm »
Sorry Skylite, I thought the reaction is endothermic. Misread it due to the bright colours D: I will read it again and give you an answer

Offline skylite

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Re: Chemistry Equilibrium Reaction Help ASAP Please!
« Reply #5 on: May 07, 2013, 02:03:59 pm »
Sry :p decided to use cyan to represent exothermic because it gives out heat so itself cool haha. Thanks in advance :D

Offline NotAbod

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Re: Chemistry Equilibrium Reaction Help ASAP Please!
« Reply #6 on: May 07, 2013, 02:12:29 pm »
Forward reaction: Exothermic
Reverse reaction: Endothermic

Now, Increasing temperature --> reaction shifts to endothermic side (In temp -> En)
why? Reaction will try to reach equilibrium again so it will shift to the side which absorbs heat, i.e. endothermic side.

Decreasing temperature --> reaction shifts to exothermic side
why? same reason, reaction will try to reach equilibrium again so it will shift to the side which gives out heat, i.e. exothermic side.


Offline NotAbod

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Re: Chemistry Equilibrium Reaction Help ASAP Please!
« Reply #7 on: May 07, 2013, 02:16:01 pm »
And Le Chatelier's Principle could help you understand better.
when there's a change in the system at equilibrium, the system will adjust to re-establish enquilibrium by counteracting (oppose) the imposed change

My teacher actually explained equilibrium to us in a funny way. If you are watching Tv and your younger brother comes and changes the channel, what would you do? counteract. how? by changing the channel back to what you were watching.
This is the same case, you increase temperature or pressure and the reaction will counteract. It will try to do the opposite of what you have done.

Offline skylite

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Re: Chemistry Equilibrium Reaction Help ASAP Please!
« Reply #8 on: May 07, 2013, 02:28:19 pm »
Ahhh i get it now! :D Thanks a lot NotAbod~!!
My confidence increased a bit  ;D

Chem paper4 tomorrow .. Good luck for everyone whose doing the same thing

Offline NotAbod

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Re: Chemistry Equilibrium Reaction Help ASAP Please!
« Reply #9 on: May 07, 2013, 03:54:37 pm »
No problem.
Good luck.