Question

A sample of NH₄HS is placed in a closed vessel and allowed to equilibrate. Calculate the equilibrium partial pressure of ammonia, assuming that some solid NH₄HS remains.

a) P(NH₃) = P(H₂S) ≠ 0
b) P(NH₃) = 0, P(H₂S) ≠ 0
c) P(NH₃) ≠ 0, P(H₂S) = 0
d) P(NH₃) = P(H₂S) = 0

Answer 1

In the equilibrium constant expression for NH4HS, the solid NH4HS is not included, and the constant is given by K = [NH3][H2S]. The concentrations of the products are inversely proportional, so if the concentration of one product increases, the other product's concentration decreases to maintain equilibrium.

Step-by-step explanation:

NH4HS does not appear in the equilibrium constant expression because it is a solid. Thus, the equilibrium constant K = [NH3][H2S], which means that the concentrations of the products are inversely proportional. If adding H2S triples the H2S concentration, for example, then the NH3 concentration must decrease by about a factor of 3 for the system to remain at equilibrium so that the product of the concentrations equals K.