Topic 6 SL - Chemical Kinetics Flashcards
species react as a results of …
collisions of sufficient energy and proper orientation
the rate of reaction is expressed as …
the change in concentration of a particular reactant/product per unit time
concentration changes in a reaction can be followed indirectly by …
monitoring changes in mass, volume, and colour
activation energy is …
the minimum energy that colliding molecules need in order to have successful collisions leading to a reaction
by decreasing activation energy, a catalyst …
increases the rate of a chemical reaction, without itself being permanently chemically changed
what occurs during the chemical reaction?
this information can be obtained from the balanced chemical equation which identifies the reactants, products, and stoichiometry
what is the extent of the chemical reaction?
this is discussed in terms of chemical equilibrium
does the reaction happen rapidly or slowly?
this is the study of rate of chemical reactions
what energy transfer is involved in the reaction? could a reaction potentially occur if given sufficient time?
analysed using the field of thermodynamics.
the change in concentration can be monitored by …
- change in pH - probe and meter
- change in conductivity - probe and meter
- change in mass or volume
- change in colour - colorimetry
the rate of reaction can be expressed in 3 ways …
1) average rate
2) instantaneous rate
3) initial rate
the average rate is …
a measure of the change in concentration of reactant or product in a given time
c/t
v/t for gasses
instantaneous rate equation
c/t = dc/dt
initial rate equation
when t = t0 the instantaneous rate = the initial rate
the rate equation is …
a mathematical differential expression, which shows rate expressed in terms of concentration
A + B –> C + D
the ideal gas equation is given by …
pV = nRT
kinetic theory of gases
1) gases consist of a large number of particles which are moving at high velocities in random directions
2) the size of the gas particle is negligible. this is an assumption.
3) collisions between one gas particle and another are completely elastic. there is no loss of energy it is simply transferred.
4) the average kinetic energy of the particles is proportional to the absolute temperature in kelvin. the movement of molecules or atoms is due to their thermal energy
collision theory
occam’s razor
1) physical contact is necessary for a reaction to occur
2) if the orientation of particles is not favourable, the reaction will not occur. if the particles have a suitable orientation the collision will be effective and this will result in a chemical reaction
homogenous catalyst
is the same physical phase or state as the reactants e.g the destruction of gaseous ozone by chlorine gas
heterogenous catalyst
is in a different phase or state from the reactants. typically, the catalyst is in the solid phase and the reactants are in the liquid or gaseous states e.g catalytic converters
maxwell boltzmann energy distribution
describes the distribution of velocities. this is a plot of the fraction of particles with a given kinetic energy (the probability of that value of kinetic energy). the representation is asymmetric.
factors that affect the rate of a chemical reaction
1) increasing the temperature at which the reaction is conducted
2) addition of a catalyst
3) increasing the concentration of the reactants
4) decreasing the particle size of reactants in the solid phase
