The effect of temperature on the equilibrium constant of a reaction can be determined using the van't Hoff equation. The van't Hoff equation relates the change in the equilibrium constant K with the change in temperature T , given the standard enthalpy change of the reaction H :ln K2/K1 = - H/R * 1/T2 - 1/T1 where K1 and K2 are the equilibrium constants at temperatures T1 and T2, respectively, and R is the gas constant 8.314 J/molK .For the reaction H2 g + I2 g 2HI g , the standard enthalpy change H is positive, as the forward reaction is endothermic requires heat . This means that the reaction favors the formation of products HI at higher temperatures and the formation of reactants H2 and I2 at lower temperatures.When the temperature increases, the equilibrium constant K will also increase, as the reaction shifts towards the products to absorb the added heat. Conversely, when the temperature decreases, the equilibrium constant K will decrease, as the reaction shifts towards the reactants to release heat.In summary, for the reaction H2 g + I2 g 2HI g , the equilibrium constant K increases with increasing temperature and decreases with decreasing temperature.