Kp is the equilibrium constant calculated based on the pressure, and it depends only on the gas substances. It will be the multiplication of partial pressures of the products raised to their coefficients divided by the multiplication of partial pressures of the reactants raised to their coefficients.
For the equation given, the stoichiometry is 1 mol of NH₃ for 1 mol of H₂S, so they will have the same partial pressure in equilibrium, let's call it p. So:
Kp = pxp
0.108 = p²
p = √0.108
p = 0.328 atm, which is the partial pressure of the ammonia.
Equilibrium means the state of reaction which there is no net changes occur it means the rate of forward reaction and rate of backward reaction become same and also it does not mean that the concentration of both side i.e. reactant and product become equal. after gaining equlibrium position the concentration of reactant and product remain same and also chemical reaction does not stop and it continues.
