Contact Process (exam Names Only) — Conditions

Industrial conditions are often compromises. For reversible reactions, equilibrium yield, reaction rate and cost must all be considered. A catalyst increases rate by lowering activation energy but does not change the equilibrium constant at a fixed temperature.

Two major examples in this chapter are the Haber and Contact Processes. For Haber: N₂ + 3H₂ ⇌ 2NH₃. Conditions balance equilibrium considerations with the need for an adequate reaction rate. For Contact: 2SO₂ + O₂ ⇌ 2SO₃. A V₂O₅ catalyst and a temperature around 450°C are commonly taught. The oxidation is reversible and exothermic, so a moderate temperature is a compromise between rate and equilibrium yield. A catalyst speeds the approach to equilibrium. It does not shift the equilibrium position or change K at a given temperature. Practical plants also consider energy use, catalyst lifetime, purification (to avoid catalyst poisoning), safety and recycling of unreacted gases.

Factories do not simply choose the condition giving the biggest theoretical yield. They also need the reaction to happen fast enough and economically. Contact: V₂O₅ at about 450°C. Catalysts speed reactions; they do not rewrite the equilibrium constant.

Temperature and pressure can affect equilibrium position, while catalysts affect how quickly equilibrium is reached. Pressure is especially relevant to gas equilibria with a change in the number of moles of gas.

Industrial optimization also considers energy consumption, reactor design, feedstock costs, catalyst lifetime, separation and recycling. The ~450°C Contact temperature is a kinetic–thermodynamic compromise, not a unique physical constant of nature.

Catalyst changes rate, not equilibrium position.