u1: collision theory and factors that effect reaction rates Flashcards
chemical systems consist of ____
particles in constant random motion at various speeds
what must a chemical reaction involve?
collisions between particles
effective collision
one that results in a reaction
what is required for an effective collision
- particles must have enough energy
- must be in correct orientation
what happens during an ineffective collision
particles rebound off one another unchanged
what is the rate of reaction dependent on?
the frequency of collision and the fraction of those collisions that are successful
reaction rate formula
reaction rate = (# of collisions)(% of effective collisions)
what factors increase the percentage of effective collisions
- higher temperature
- higher concentration
- more surface area
- presence of catalyst
- nature of reactants (i.e. liquid v. powder)
transition state/activation complex
- short-lived, unstable structure formed during successful collision where new bonds form nd old ones break
- always higher in energy than products/reactants
activation energy (Ea)
- diff. in energy between reactants and transition state
- min. amnt. of energy needed for activation complex to form
how is activation energy (Ea) related to speed of reaction
- smaller = faster
- larger = slower
reaction mechanism
process by which a reaction occurs
how do catalysts speed up reactions
- add catalyszed reaction pathway which needs lower activation energy than uncatalyzed
- may be single or many steps
what increased the rate of a reaction
- smaller container
- increase number of particles
- speed up particles by adding heat
- break up clumps into individual particles
- use catalyst
reactions between ions v. molecules
- ions are faster bc no bonds to break and opposite ions attract each other
- molecules slower bc. covalent bonds need to be broken but more energy released than used
