Air and water pollution
Common air pollutants include carbon monoxide (from incomplete combustion), sulfur dioxide (from burning fuels containing sulfur impurities), and oxides of nitrogen (from vehicle engines at high temperature). Water pollution comes from sources like industrial waste, sewage, and agricultural runoff (fertilizers and pesticides), which can cause excessive algae growth (eutrophication) that starves water of oxygen.
The greenhouse effect and acid rain
Carbon dioxide and methane trap heat radiating from the Earth's surface, warming the atmosphere -- a natural process made stronger by human activity like burning fossil fuels. Separately, sulfur dioxide and nitrogen oxides dissolve in atmospheric moisture to form dilute sulfuric and nitric acids, falling as acid rain that damages plants, buildings, and aquatic ecosystems.
The Haber process
The Haber process manufactures ammonia from its elements: . It uses a moderately high temperature and high pressure, with an iron catalyst to speed up reaching equilibrium -- ammonia is a key raw material for nitrogen-based fertilizers.
Example 1: Why is the Haber process reaction written with a reversible arrow, ?
Because the reaction doesn't go to completion -- under the reaction conditions, ammonia can also decompose back into nitrogen and hydrogen, so the system reaches a dynamic equilibrium rather than fully converting all reactants to product.
The Contact process
The Contact process manufactures sulfuric acid. Sulfur is burned to form sulfur dioxide, which is then oxidized (using a vanadium(V) oxide catalyst) to sulfur trioxide, which is finally reacted with water (via an intermediate step) to form concentrated sulfuric acid -- one of the most widely used industrial chemicals, for fertilizers, detergents, and more.