Catalysts, activation energy and industrial processes

Last time

Before we start: last time, in Le Chatelier's principle and acid-base titration curves, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Feeding the world with air

About half of the nitrogen in your body once passed through a Haber process plant. The process turns nitrogen from the air into ammonia, for fertiliser. It works only because a catalyst and carefully chosen conditions balance two competing needs: a good yield, and a fast enough rate.

Catalysts

A catalyst increases the rate of a reaction by providing an alternative pathway with a lower activation energy. It is not used up. A catalyst does not change the enthalpy change, the position of equilibrium, or the value of the equilibrium constant. A heterogeneous catalyst is in a different phase from the reactants, such as solid iron with gases. A homogeneous catalyst is in the same phase. A catalyst lets a process work at a lower temperature, saving energy and cost.

Pathway diagrams with catalysts

Draw the uncatalysed route with a high peak. Then draw the catalysed route with a lower peak, from the same reactants to the same products. The reactants and products are at the same levels, so delta H is the same. Only E A changes. Label the two routes, and mark each activation energy with an arrow from the reactants.