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MDCAT Prep · Chemistry · Quick Reference
Lesson 10 — Equilibrium Cheat Sheet
In one line: Le Chatelier's principle predicts which way equilibrium shifts when you change concentration, temperature, or pressure — a catalyst changes speed only, never position.
Key Ideas
1Equilibrium. Forward = reverse rate. Concentrations constant, not equal. Kc = [products]/[reactants].
2Kc value. Kc > 1 favours products; Kc < 1 favours reactants.
3Concentration shift. Adding product shifts equilibrium left (toward reactants).
4Temperature shift. Raising T shifts equilibrium in the endothermic direction.
5Pressure & catalyst. Higher P shifts toward fewer gas moles; a catalyst speeds both directions equally — no shift.
Haber Process Worked Example
N2 + 3H2 ⇌ 2NH3
Temperature
~400°C
Pressure
~200 atm
Catalyst
Iron
Why 400°C (compromise)
Higher T speeds rate but shifts equilibrium away from NH3 (exothermic)