kinetics 1 Flashcards
(18 cards)
what does Maxwell-Boltzmann distribution show
the spread of molecular kinetic energies for a gas at a specific temperature
how to catalysts speed up reactions
provide alternate pathway
homogeneous catalysts
catalysts in same phase as reactants
what is a phase
could mean different physical states, but some in same state can be different phases e.g. liquids that don’t mix hexane and water
heterogenous catalysts
different phase to reactants - usually solid and used in industry
how to heterogenous catalysts work
- adsorption - correct orientation and bonds in reactant weaken
- reaction occurs on surface of catalyst
- desorption - product leaves
why are catalysts used in industry
they require less energy so cheaper
what is collision theory
if two molecules collide they can react; they must
- collide with sufficient energy to cause a reaction (activation energy)
- collide in the correct orientation as some groups can cause steric hindrance
how does surface area affect rate of reaction
(only reactions with solid reactant)
large SA results in higher RR (reactions occur on surface therefore larger SA means more particles exposed so frequency of collisions increases)
how does concentration affect rate of reaction
rate of reaction increases as concentration increases
more reactant particles in a give volume means more frequent collisions
how does temperature affect the rate of reaction
increases it - particles have more kinetic energy so collide more frequently and collide with more energy so more collisions have energy greater than the activation energy
rate of reaction equation
concentration product / time
how to deduce the rate at a specific time on a graph
draw a tangent
how to determine intial rate of reaction
draw steepest tangent (through origin), determine gradient of tangent
how to draw a Maxwell Boltzmann curve
curve must start at origin, must not be symmetrical, must not touch x axis on right hand side, area under curve represents total number of particles
how does Maxwell Boltzmann curve change with increase in temperature
area under curve stays the same, shifts to the right, more particles with energy greater than Ea
how do catalysts affect Maxwell Boltzmann curve
curve stays the same, Ea decreases (so line shifts left) as provides alternate reaction pathway with lower Ea
