Rates of reaction and equilibrium

Factors affecting rate (collision theory)

• Concentration: more particles, more collisions.
• Temperature: particles move faster and more collisions have the activation energy.
• Surface area: powders react faster than lumps.
• Catalyst: provides an alternative path with lower activation energy; not used up.
• Pressure (gases): like increasing concentration.
• Light: for some reactions (photosynthesis, silver halides on film).

Measuring rate

Volume of gas over time, loss of mass, time for a cross to disappear (sodium thiosulphate and acid).