Equilibrium constants and increasing yield

For a reaction at equilibrium, the equilibrium constant (K) compares the amounts of products and reactants. For the general reaction aA + bB <=> cC + dD, K = [C]^c [D]^d / ([A]^a [B]^b), where square brackets mean concentration in moles per liter and pure solids and liquids are left out. A large K, much greater than 1, means that at equilibrium the mixture is mostly products; a small K, much less than 1, means it is mostly reactants. For a given reaction, K stays the same at a given temperature no matter what amounts you start with, and it changes only when the temperature changes. Le Chatelier's principle shows how chemists can raise the yield of a product. The Haber process, which makes ammonia for fertilizer from nitrogen and hydrogen (N2 + 3 H2 <=> 2 NH3), is a classic example: high pressure favors the side with fewer gas molecules, the ammonia side, and removing ammonia as it forms pulls the reaction toward making more. Because the forward reaction is exothermic, a lower temperature would favor ammonia, but it would make the reaction far too slow, so industry uses a moderate temperature and an iron catalyst as a compromise between yield and speed.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report