Chemical equlibrium problem?

at a certain temperature a mixture of hydrogen and iodine was prepared by placing 0.500 moles of hydrogen and 0.500 moles of iodine in a one liter flask. After some time, the quilibrium was establshed write the balances equation of tis reaction at equklibrium. after a while the iodoine concentration dropped to 0.050 mol dm-3. what is the value of Kc (show all work)