Suppose that the formation of mullite from a mixture of alumina and silica powders is a diffusion-controlled process. How would you prove it? If the activation energy is 50 kcal/mole and the reaction proceeds to 10% of completion at 1400°C in 1 hour, how far will it go in 1 hr at 1500°C? and in 4 hr at 1500°C?.