Question

The reaction CH₄(g) + 2 H₂S(g) ↔ CS₂(g) + 4 H₂(g) has an equilibrium constant of 2.73 at a specific temperature. The initial concentrations of the reactants and products are [CH₄] = [CS₂] = 0.200 M and [H₂S] = [H₂] = 0.600 M. What is the equilibrium concentration of the H₂ if, at equilibrium, [CH₄] = 0.150 M?

Answer 1

construct the ICE table

                CH₄(g)    + 2 H₂S(g)      ↔ CS₂(g)    +     4 H₂(g)

I                 0.2                  0.6                       0.2                  0.6

C               -x                     -2x                     +x                    +4x

E              0.2-x                 0.6-2x                0.2+x                0.6+4x

he has given equilibrium concentration of CH4

= [CH4] = 0.15  

but from ICE table equilibrium concentration of CH4 = 0.2-x

0.2-x = 0.15

x = 0.2 - 0.15 = 0.05M

now equilibrium concentratiof H2 from ICE table

[H2] = 0.6 + 4x

put the above obtained x value here

= 0.6 + 4 (0.05)

= 0.6 + 0.2

[H2] at equilibrium= 0.8M