Chemistry unit 8

Rate

a change that occurs over a time interval(speed or velocity)

Rate of reaction

the speed of a chemical reaction

calculating rate of chemical reactions

(Xfinal-Xinitial) / (Timefinal-Timeinitial)

events for a collision to occur

• X2 and Y2 must collide

• X-X bond break

• Y-Y bond break

• X-Y bonds form

Activation energy

minimum amount of energy needed for a reaction to occur

more effective collision →

faster reaction rate

less effective collision →

slower reaction rate

reactants

starting materials

products

ending materials

intermediates

materials made along the way

transition state

intermediate of highest energy

• top of hill in diagrams

• very energetic and unstable

reaction energy

difference between energy of reactants and energy of products

activation energy

difference between energy of reactants and energy of transition state

low activation energy →

small hill→ easy reaction → fast reaction rate

high activation energy→

big hill→ hard reaction→ slow reaction rate

lower concentration

• less collisions, slower rate

higher concentration

• more collisions, faster rate

lower pressure

• particles are farther, less collision, faster rate

higher pressure

particles are closer, more collisions, faster rate

low temp

lower kinetic energy, less collide, slow rate

high temp

high kinetic energy, more collide, fast rate

without catalyst

• large activation rate, slower rate

with catalyst

• small activation rate, fast rate

reversible reactions

reaction occur in either direction(two arrows)

equilibrium

rates of reverse processes are equal

systems that have reached equilibrium are dynamic

they keep happening

endothermic

energy required

exothermic

energy released

aA+bB ←→ cC+dD

K= (C)^c(D)^d / (A)^a(B)^b

if K>1

product-favored

if K<1

reactant-favored

add

away

remove

towards