Ammonium bisulfide decomposes according to NH₄HS(s) ⇌ NH₃(g) + H₂S(g). Which expression gives Kp for this equilibrium?

Core Concept

Equilibrium constants multiply each gas partial pressure raised to its coefficient. Both products carry coefficient 1, so their pressures simply multiply in the numerator. Ammonium bisulfide is a pure solid whose effective concentration never changes, so it is omitted entirely. Only NH₃ and H₂S therefore remain in the expression.