Kinetics Flashcards
what is kinetics
how quickly a reaction runs
kinetics vs thermodynamics
kinetics controls what happens during a reaction and the amount of product obtained after a specific time while thermodynamics controls what happens at the end of a process and the amount of product obtained eventually
collision theory
reactions occur when molecules collide, producing kinetic energy
- the rate of reactions depends on collisions
factors controlling reaction rate
= factors controlling collision efficac
1. concentration: collision frequency - higher concentration = more molecules colliding = higher rate
2. temperature: kinetic energy - higher temp = more molecules at a higher kinetic energy = moving faster = higher rate
3. molecular structure: collision orientation - molecules must collide at their reactive sites
- insignificant for symmetrical molecules
transition states
a high energy intermediate state occurring for an infinitely short time following successful collision
- not usually observable
if [initial] doubles for one reactant and the others stay constant, the initial rate …
0 order: doesn’t change
1st: doubles
2nd: quadruples
3rd: x8
rate constant (k)
proportionality constant that relates concentration and orders to observed rate
- stays fixed regardless of rate throughout reaction
effects of k size on rate
larger k = faster reaction
k units
L^(x-1)mol^(1-x)S^-1 x = order
catalysts
substances that increase reaction rate without being consumed by the reaction since they participate but get regenerated at the end
activation energy
= transition state energy = rate determining step
- lowered by catalysts
homogenous catalysts
same phase as reactants
interferes with reactant to form intermediate substance which then decomposes or reacts with another reactant to regenerate original catalyst and form products
heterogenous catalyst
= present in a different phase (typically solid for liquid and gas) than reactants
- typically functions by furnishing an active surface for the reaction to occur
