NH3(g) and H2S(g). At 25°C, some NH4HS(s) is placed

in an evacuated container. A portion of it decomposes,

and the total pressure at equilibrium is 0.659 atm. Extra

NH3(g) is then injected into the container, and when equilibrium

is reestablished, the partial pressure of NH3(g) is

0.750 atm.

(a) Compute the equilibrium constant for the decomposition

of ammonium hydrogen sulfide.

(b) Determine the final partial pressure of H2S(g) in the

container.

For (a), I assumed that the partial pressures of NH3 and H2S are equivalent since they have the same stoichiometry coefficient and divided the total pressure at equilibrium of 0.659 atm by 2 to find the partial pressures.

I am not sure how to approach (b). Do I assume the partial pressures of NH3 and H2S are equivalent again?