Factors Affecting ReactionRates

FACTORS AFFECTINGREACTION RATE

There are five factors affecting rate:

P Chemical nature of reactants

P Concentration of reactants

P Temperature

P Presence of a catalyst

P Surface area

Chemical Nature of Reactants

P simple atoms/ions reactmuch faster than morecomplex ones

P due to the number of bondsthat need to be broken andreformed Potassium

metal

Calcium metal

Video

Concentration

P if the initialconcentration ofreactants in areaction isincreased, generallythe rate of reactionincreases

P this is due to thenumber ofatoms/moleculesthat are available toreact

Temperature

P as the temperature of a systemincreases, the rate of reactionincreases

P this is due to an increase inkinetic energy within theatoms/molecules, which allowsthem to move faster/farther,making the contact with theother atoms/molecules that isnecessary for the reaction toproceed

P general rule of thumb is: a 10E Cincrease in temperature resultsin a double or triple rate ofreaction (at SATP)

Presence of a Catalyst

P catalyst - is a substance thatalters the rate of a chemicalreaction without itself beingpermanently changed.

P most catalysts have beendiscovered by trial and error

P examples include catalyticconverters in car engines;chlorophyll is the catalystduring photosynthesis;enzymes in biologicalprocesses

Surface Area

P as the surface area of thereactants are increased, therate of reaction increases

P during a heterogeneousreaction, the reaction occurswhere the two phasesactually come into contactwith each other.

P therefore, when more surfacearea of one of the reactants isexposed and comes intocontact with the otherreactant, the rate of thereaction will increase

Homework:

Read pages 367 -370

Complete # 3 - 6 (Practice) pg. 371

# 1 (Section Questions) pg. 371