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Oddveig science forum beginner
Joined: 11 Jan 2006
Posts: 4

Posted: Sun Mar 05, 2006 1:04 pm Post subject:
Equilibrium....?



I have the following equation:
2NH3 <>N2+3H2
Starting with an empty container,adding 0,500mol NH3,at equilibrium we've
got left 0,100mol NH3.
What is the equilibriumconstant for this reaction?
When I'm doing the equation,I'm getting 0,400
The correct answer is however 0,423.
What am I doing wrong? 

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Oscar Lanzi III science forum Guru Wannabe
Joined: 30 Apr 2005
Posts: 176

Posted: Mon Mar 06, 2006 2:12 am Post subject:
Re: Equilibrium....?



You consume 0.400 mol NH3 to go down from 0.500 mol to 0.100 mol. So
how many moles of H2 do you form, and how many moles of N2 do you form?
Now put those numbers into the expression for the equilibrium constant.
Here's a hint: when I do it I get NEITHER 0.400 nor 0.423. Methinks
there is a typo somewhere.
OL 

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Lasse Murtomäki science forum beginner
Joined: 17 Jun 2005
Posts: 35

Posted: Mon Mar 06, 2006 8:34 am Post subject:
Re: Equilibrium....?



Initial amount of NH3 = n0 = 0.5 mol
At equilibrium the amount of NH3 = n0  2x = 0.1 mol => x = 0.2 mol
At equilibrium the amount of H2 = 3x = 0.6 mol
At equilibrium the amount of N2 = x = 0.2 mol
K = [0.2*(0.6)^3]/(0.1)^2 = 4.32
If the equilibrium constant is defined as I did above.

Dr. Lasse Murtomäki
Helsinki University of Technology
lasse.murtomaki@tkk.fi 

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