Question

Consider the reaction: NH4HS(s)⇌NH3(g)+H2S(g) An equilibrium mixture of this reaction at a certain temperature was found to have [NH3]= 0.238 M and [H2S]= 0.305 M . Part A What is the value of the equilibrium constant at this temperature?

Answer 1

First, let us define the equilibrium constant for any species:

The equilibrium constant will relate product and reactants distribution. It is similar to a ratio

The equilibrium is given by

rReactants -> pProducts

Keq = [products]^p / [reactants]^r

For a specific case:

aA + bB = cC + dD

Keq = [C]^c * [D]^d / ([A]^a * [B]^b)

Special notes:

Typically; we use aqueous and gas phases. (Gases and Aqueous Concentrations can be related via PV = nRT, since M = n/V as well)

Solids and Liquids, i..e. (s) and (l) have activity of 1. Therefore, they must not be considered in the ratios.

then

Kc = [NH3][P-H2S] / (NH4HS)

(P-NH4HS) = 1

K = P-NH3 * P-H2S

in equilbirium

Kc = 0.238*0.305

Kc = 0.07259