At a particular temperature a 2.0 liter flask contains 2.0 mol of H2S, 0.40 mol of H2, and 0.80 mol of S2. Calculate the equilibrium constant for the reaction:

2H2(g) + S2(g) <--> 2H2S(g)

I will assume that you want the equilibrium constant Kc, which is based upon concentrations [ ] in moles/liter. The coefficient Kp , based upon partial pressures in atm, could also be determined if the total pressure had been provided.

Kc = [H2S]^2/{[S2][H2]^2}
= 1.0^2/[0.4*(0.2)^2]
= 1/[(0.4)(0.04)] = 62.5 liter/mole

To calculate the equilibrium constant (K) for the given reaction, we need to use the concentrations of the reactants and products at a particular temperature.

The reaction is given as:
2H2(g) + S2(g) ⇌ 2H2S(g)

First, we need to determine the initial concentrations of the reactants and products. We are provided with the number of moles for each species and the volume of the flask. Since all the moles are given in molar units, we can directly use them as concentrations.

Initial concentrations:
[H2] = 0.40 M
[S2] = 0.80 M
[H2S] = 2.0 M

Now, we can write the equilibrium expression using the concentrations:
K = [H2S]^2 / ([H2]^2 × [S2])

Substituting the given values:
K = (2.0)^2 / ((0.40)^2 × 0.80)

Simplifying:
K = 4.0 / (0.16 × 0.80)
K = 4.0 / 0.128
K ≈ 31.25

Therefore, the equilibrium constant for the reaction is approximately 31.25.