[vverityv]

I'm having trouble with this problem:

"A solution contains the relatively insoluble solid M₂X(s) with K_sp = 8.89 x 10^-25.  A secondary equilibrium occurs when CN^- is added with K_formation M(CN)₆ = 1.76 x 10¹⁶.  Write the overall equilibrium equation and calculate K_net for M(CN)₆  Write result with 3 s.f."

So basically this is what I'm getting:

M₂X + H₂O  M⁺ + 2X^-  K_sp= 8.89 x 10^-25
M⁺ + 6CN^-  M(CN)₆   K_formation= 1.76 x 10¹⁶
_____________________________________
M₂X + H₂O + 6CN^-   M(CN)₆ + 2X^-  K_net

K_net= K_sp x K_formation
K_net= (8.89 x 10^-25) x (1.76 x 10¹⁶)
K_net=0.0000000156

But the correct answer for K_net is 16,594

Can anyone tell me what I'm doing wrong??

[Hunter2]

The equations are not balanced. I dont think M(CN)₆ is existing, but maybe a  [M(CN)₆]^4-

[vverityv]

The "M" is just suppose to represent some metal ion.  If the overall charge of the compound is a charge different than +1 is that suppose to somehow change K_formation?

[Borek]

M₂X + H₂O  M⁺ + 2X^-

Remove water (it doesn't react) and balance the equation.

In general you have to write correct reaction quotients for all three reactions and see how to express the third with two first. That's not what you did so far - just multiplying both constant doesn't yield what you need.

[vverityv]

Okay, I took water out and fixed the equation:

M₂X  2M⁺ + X^-2

but I still don't see how that affects K_sp or K_formation

[Borek]

Have you wrote all three reaction quotients? Do it. See what combination of the first two gives the third.