I am having trouble with the following question my workings come to an
answer of 5.10 but this is clearly incorrect I got to this via the
following..

 [NOCl]2           0.454
 -------     =     -----     = 5.10
[NO]2[Cl2]         0.089

Question:

For the following system at equilibrium:

2NO(g) + Cl2(g) - Eq - 2NOCl(g)

0.416 mol NO, 0.515 mol Cl2 and 0.311 mol NOCl are found in a 1.0L
container at 25oC.

Calculate the equilibrium constant, K, at 25oC.

Answer:

a) 2.82   b)3.49   c)0.921   d)1.09

Please show me the workings on how you got to your answer. Cheers.

Hi!!


What is equilibrium constant (K)?
It is a constant at a given temperature such that when a reversible
chemical reaction aA + bB = cC + dD has reached equilibrium. It is
given by the following formula:
       [C]^c  *  [D]^d  
K = ----------------------
       [A]^a  *  [B]^b 


Where [X] is the molar concentration of the reactants and products
(moles of solute per litre of solvent).



For this problem you have:
- A system at equilibrium:

2NO(g) + Cl2(g) - Eq - 2NOCl(g) ;

with 0.416 mol NO, 0.515 mol Cl2 and 0.311 mol NOCl in a 1.0L container at 25°C.
The above means that:
[NO] = 0.416
[Cl2] = 0.515
[NOCl] = 0.311

Then:
K = (0.311^2) / (0.515 * 0.416^2) =
  = (0.097) / (0.089) =
  = 1.09


For further reading and examples see:
"Equilibrium Constant":
http://www.cartage.org.lb/en/themes/Sciences/Chemistry/Inorganicchemistry/Equilibrium/Equilibrium/Equilibrium.htm

"ChemTeam: Calc of Equilibrium Constant":
http://dbhs.wvusd.k12.ca.us/webdocs/Equilibrium/Calc-K-from-equilib-conc.html

"Calculating_Equilibrium_Constants":
http://www.chem.purdue.edu/gchelp/howtosolveit/Equilibrium/Calculating_Equilibrium_Constants.htm



Search strategy:
"equilibrium constant" chemical
"Molar concentration" equilibrium


I hope this helps you. Feel free to request for a clarification if you need it.

Regards,
livioflores-ga

I can't believe I make a silly mistake like that :)
Thanks for your help great answer. Cheers.