0.50 mol of $I_2$ (g) and 0.50 mol of $Br_2$ (g) are placed in a closed flask. The following equilibrium is established.

0.50 mol of $I_2$ (g) and 0.50 mol of $Br_2$ (g) are placed in a closed flask. The following equilibrium is established.

$I_2 (g) + Br_2 (g) \rightleftharpoons 2IBr (g)$

The equilibrium mixture contains 0.80 mol of IBr (g). What is the value of $K_c$?