chemistry

The equilibrium constant

V_forward = k_forward x [I₂] x [H₂]

and
V_backward = k_backward x [HI]²

We know that at equilibrium, the forward and the backward reaction occur in the same rate:

V_forward = V_backward

Or:

k_forward x [I₂] x [H₂] = k_backward x [HI]²

kforwardbackward (1K)

Att.: the quotient of the two constants gives one new constant; we may write:

K is called: "the equilibrium constant"