Question

Consider the reaction for the decomposition of hydrogen disulfide: 2H2S(g)⇌2H2(g)+S2(g), Kc=1.67×10−7 at 800∘C The reaction is carried out at the same temperature with the following initial concentrations: [H2S][H2][S2]===1.20×10−4M0.00M0.00M Find the equilibrium concentration of S2. Express the concentration to three significant figures and include the appropriate units.

Answer 1

        2H2S(g) ? 2H2(g) +   S2(g)

I      1.2*10^-4       0                0

C      -2x               2x               x

E     1.2*10^-4 -2x 2x               x

Kc   = [H2]^2[S2]/[H2S]^2

1.67*10^-7   = (2x)^2*x/(1.2*10^-4 -2x)^2

1.67*10^-7 *(1.2*10^-4 -2x)^2   = (2x)^2*x

       x   = 7.7*10^-6

    [S2]   =x = 7.70*10^-6 M