[Rek]

Hi, saw this site on the SOSmath.com forums and need help. So here I am : )

This problem is giving me trouble. I think it may be the wording...but I don't really know where to start, so any help would be appreciated!  Here it is:

At 25* C in a closed system, ammonium hydrogen sulfide exists as the following equilibrium:  NH₄HS(s) <==>NH₃(g) + H₂S(g)

When a sample of pure NH₄HS is placed in an evacuated reaction vessel and allowed to come to equilibrium at 25* C, total pressure it .660 atm.  What is the value of Kp.

Like I said, I don't really know where to start.  I don't know what to asssume the amount of the inital species is or if that's the right method.  Thanks for the *delete me*

[plu]

Try writing out the equilbrium expression for the reaction first