Chem- Topic 6/ 16

• Rate of reaction is

  the increase in concentration of a product per unit time.
• Dilute meaning

  a substance to have very little moles compared to the amount of liquid it is being submerged in.
• Kinetic Molecular theory

  a model of gas particles, neglecting attractive and repulsive forces, collisions of particles are elastic, particles are constantly in motion and temperature increase is proportional to average kinetic energy increase
• When will a reaction occur according to collision theory

  particles collide with min. required activation energy and with the proper geometry.
• Greater concentration means what in relation to collision frequency? 


   more collisions per unit time, thus faster rate.
• according to collision theory, Greater temperature means that

  more particles and collisions per unit time with the minimum amount of activation energy, thus more particles able to react and faster reaction
• according to collision theory, greater pressure means 


  more collisions per unit time, thus faster rate.
• according to collision theory, greater surface area means,

  more collisions per unit time, thus faster rate
• what is a catalyst?

   a substance that speeds up a reaction by providing an alternative path with lower activation energy (does not actually lower Ea). it will increase the rate of chemical reaction without it permanently being chemically changed.
• Homogenous catalyst 


  same state as the reactants
• heterogenous catalyst

  different state as the reactant
• FOR a Maxwell-boltsman curve, greater temperature means, 


  curve flattens so more particles have a higher energy, thus more particles have the minimum Ea or greater.
• for a Maxwell-Boltzmen graph what is on its x and y axis?

  x: Kinetic energy y: Probability density
• How can reaction rate be experimentally determined?

  light absorption, collecting evolved gas, change in mass (gas), pH, titration, change in pressure (gas to gas)
• Rate of a chemical reaction is equal to the rate constant when

  a reaction is ZERO order
• if the concentrations are halved the rate constant would...

  remain the same
• what factors affect reaction rate?

  the state of the reactants, the frequency of the collisions between particles and the average kinetic energy of the particles
• Order of reaction

  the relationship between the concentrations of species and the rate of a reaction
• What does zero order mean?

  concentration of reactant has no affect on rate
• slope of rate v. concentration graph (for zero order)

  rate constant k
• First order 


  concentration of reactant is directly proportional to rate
• Second order

  rate is promotional to square concentration.
• Overall order

  sum of reactants orders of reaction.
• IF A CATALYST IS USED --

  count in the overall order of reaction
• Unit of k will depend on order of reaction but, 


  time will always be to a negative one power.
• Rate units will always be

  mol per dm3 per second
• Relationship between k and temp

  as temp increases, k increases exponentially
• the larger the constant k, the rate is 


  faster
• what is hals-life independent of?

  concentration for first order reactions
• For first order if one of the reactants have their concentration halved, rate will...

  also half
• for second order if one of the reactants have their concentration halved, rate will be 


  divided by four
• Rate determining step

  the step in a run that has the highest activation energy theory is the lowest and determines the overall speed of a reaction.
• what are intermediate species

  molecules created for a finite amount of time during a reaction in between activation energies where energy is lowest and are formed in one step then comsumed in the next.
• Transition states/activated complexes are 

  molecules that only have a transient existence where bonds are half broken and half made at the highest points of potential energy.
• What has no effect on activation energy

  greater temperature
• In terms of RDS, if a reactant has 0 order this means 

  the substance reacting is not involved in the first RDS.
• Unimolecular 


  a step involving one reacting molecule
• unimolecular mechanisms have more than one 


  activated complex.
• Bimolecular 


  a step involves 2 reacting molecules
• Bimolecular mechanisms have no intermediate, only a 


  activated complex