Reaction Rates Speed matters! *Watch a Video!*

Reaction Rate Decrease in concentration of reactants with time or Increase in concentration of products with time ∆ [reactant or product] M mol/L ∆ time s s ==

Reaction Rate Example : [Products] Increase [Reactants] Decrease H 2 + I 2  2 HI

Reaction Rate Example [HI] at time t 2 – [HI] at time t 1 ∆ [HI] t 2 – t 1 ∆ t 0.09 M – 0.08 M 0.01 M 7 s – 5 s 2s = = = M/s

Factors affecting Reaction Rates Temperature Concentration Pressure Surface Area Catalyst

Temperature Increasing temperature generally increases reaction rates. Increasing temperature increases the average kinetic energy of particles → reactant particles collide more frequently Increasing temperature by 10 K can double a reaction rate.

Concentration & Pressure As concentration increases, reaction rate increases. Increasing concentration increases the collision frequency. For Gas reactants, increasing Pressure increases the concentration of a gas, thus increasing the reaction rate.

Surface Area Increasing the surface area of solid reactants increases the opportunity for collisions, speeding up the reaction. Crushing solids increases the surface area, speeding up the reaction.

Catalysts speed up a reaction, not being used!

Catalyst & Activation Energy