Consider the gas-phase reaction H₂(g) + I₂(g) ⇄ 2 HI(g)
Suppose that a sealed flask containing H₂ and I₂ has been heated to 425 °C and the initial concentrations of H₂ and I₂ were each 0.0175 mol/L. With time, the concentrations of H₂ and I₂ decline, and the concentration of HI increases. At equilibrium [HI] = 0.0276 mol/L. Use this experimental information to calculate the equilibrium constant.