Question

For the following reaction, nh4hs(s)⇌nh3(g) H₂S(g), what is the equilibrium expression?

1) Kc = [NH₃][H₂S]/[NH₄⁺HS]
2) Kc = [NH₄⁺HS]/[NH₃][H₂S]
3) Kc = [NH₃][H₂S]
4) Kc = [NH₄⁺HS]

Answer 1

The correct equilibrium expression for the decomposition of NH4HS(s) is Kc = [NH3][H2S], excluding the solid reactant from the expression.

Step-by-step explanation:

The correct equilibrium expression for the given reaction NH4HS(s) ⇌ NH3(g) + H2S(g) is Kc = [NH3][H2S]. According to the rules for writing equilibrium constant expressions, solids are not included, and only the concentrations of gaseous and aqueous species are part of the expression.

Therefore, option 3) Kc = [NH3][H2S] is correct. It is important to understand that the concentrations of the products (NH3 and H2S) are inversely proportional at equilibrium. If the concentration of one of these gases is increased, the other must decrease to maintain the value of Kc.