[mrlucky0]

Consider the following endothermic reaction:

NH4HS (s)  NH3 (g) + H2S (g)

If the system were at equilibrium within a sealed container, which of the following would produce additional H2S?

I. ...
II. Adding more NH4HS
III. ...

I don't understand why adding more NH4HS would NOT affect the equilibrium and produce additional H2S. It's a solid, but nevertheless, from Le-Chatelier's principle,  adding more reactant will shift the equilibrium to the right, correct? If we assume that the equilibrium for this reaction is such that ALL the NH4HS has turned into it's gaseous products NH3 and H2S, then surely, adding more NH4HS would produce more H2S right?

Can someone explain to me why I might be wrong? 

[AWK]

If we assume that the equilibrium for this reaction is such that ALL the NH4HS has turned into it's gaseous products NH3 and H2S, then surely, adding more NH4HS would produce more H2S right?

Then this is not the equilibrium. Equilibrium needs some solid NH4HS is present but for calculations you use obly gaseous reagents.