The reaction H₂(g) + I₂(g) ⇌ 2 HI(g) has Kc = 22.0 at a certain temperature. A 1.00 L vessel initially contains 1.00 mol of H₂, 1.00 mol of I₂, and no HI. At equilibrium the concentration of I₂ is 0.300 M. Calculate the equilibrium concentration of HI.