[aziza]

Hello, I'm trying to solve this equilibrium question and it's frustrating me to no end:

Reaction: Ni(s) + 4CO(g) <--> Ni(CO4)(g)    Kc=1.8x10¹¹

The question is: Initially 0.010 mol/L of Ni(CO4) is placed in a closed container with solid nickel, no CO is present.  Calculate the equilibrium concentrations of CO and Ni(CO4).

Here's the work I did:

                         4CO  <--->  Ni(CO4)
                 I       0.00           0.010
                C       +4x            -x
                E       +4x           0.010 - x

Then:
Kc = (0.010-x)/(4x)⁴=1.8x10¹¹
      0.010 - x = (1.8x10¹¹)(256x⁴)
      0 = 4.61x10¹³x⁴ + x - 0.010

Can't put that into a quadratic, so I guess I have to use a simplifying assumption and/or successive approximation, but I'm a bit confused as to how to proceed with that. 

Any help would be greatly appreciated!


Regards,

M

[enahs]

This site will show you how to actually solve it using logarithms or roots if you are really good at algebra and can simplify the equation down; which is not always possible, this case is not worth the effort. It also has the successive approximation method as well.

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

[Borek]

Kc = (0.010-x)/(4x)⁴=1.8x10¹¹

Are you sure you have not exchanged products and reactants?

[AWK]

      0 = 4.61x10¹³x⁴ + x - 0.010

Neglect x as a first approximation
4.61x10¹³x⁴ = 0.010

[champ]

assume that x<< .0100
 Kc= 0.0100/(4x)^4
and slove for the "x".