To explain what chemical kinetics does, I use the reaction (1.1) N 2 + 3 H 2 → 2 NH 3 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429258947/2e36ab18-b66f-4149-a539-bb798d93c7f5/content/eq1.tif"/> as an example. A mixture of N₂ with H₂ held at high temperature and pressure, in the presence of the right catalyst, produces ammonia. After mixing the reactants, the number of moles of ammonia increases in time and those of nitrogen and hydrogen decrease. Chemical kinetics studies how fast the amounts of reactant and product change during a reaction.