Cu 4 3 The Kc for the reaction of hydrogen and iodine to pro

C.u) 4 3. The Kc for the reaction of hydrogen and iodine to produce hydrogen iodide equals 54.3 at 430°C. Calculate the equilibrium concentrations of H, I,, and HI if the initial concentra- tions are [HJ = [12] = 0 M, and [HI] = 0.525 M. 2. 53

Solution

3)          H2(g) + I2(g) <----> 2HI(g)

   initial 0        0            0.525 M

   change   +x       +x            -2x

   equil     x        x           0.525-2x

   Kc = [HI]^2/[H2][I2]

54.3 = (0.525-2X)^2/(X*X)

X = 0.056

At equilibrium,

[H2] = X = 0.056 M

[I2] = X = 0.056 M

[HI] = 0.525-2*0.056 = 0.423 M