Topic 6 SL - Chemical Kinetics

Question 1

species react as a results of …

Answer 1

collisions of sufficient energy and proper orientation

Question 2

the rate of reaction is expressed as …

Answer 2

the change in concentration of a particular reactant/product per unit time

Question 3

concentration changes in a reaction can be followed indirectly by …

Answer 3

monitoring changes in mass, volume, and colour

Question 4

activation energy is …

Answer 4

the minimum energy that colliding molecules need in order to have successful collisions leading to a reaction

Question 5

by decreasing activation energy, a catalyst …

Answer 5

increases the rate of a chemical reaction, without itself being permanently chemically changed

Question 6

what occurs during the chemical reaction?

Answer 6

this information can be obtained from the balanced chemical equation which identifies the reactants, products, and stoichiometry

Question 7

what is the extent of the chemical reaction?

Answer 7

this is discussed in terms of chemical equilibrium

Question 8

does the reaction happen rapidly or slowly?

Answer 8

this is the study of rate of chemical reactions

Question 9

what energy transfer is involved in the reaction? could a reaction potentially occur if given sufficient time?

Answer 9

analysed using the field of thermodynamics.

Question 10

the change in concentration can be monitored by …

Answer 10

1. change in pH - probe and meter
2. change in conductivity - probe and meter
3. change in mass or volume
4. change in colour - colorimetry

Question 11

the rate of reaction can be expressed in 3 ways …

Answer 11

1) average rate
2) instantaneous rate
3) initial rate

Question 12

the average rate is …

Answer 12

a measure of the change in concentration of reactant or product in a given time
c/t
v/t for gasses

Question 13

instantaneous rate equation

Answer 13

c/t = dc/dt

Question 14

initial rate equation

Answer 14

when t = t0 the instantaneous rate = the initial rate

Question 15

the rate equation is …

Answer 15

a mathematical differential expression, which shows rate expressed in terms of concentration
A + B –> C + D

Question 16

the ideal gas equation is given by …

Answer 16

pV = nRT

Question 17

kinetic theory of gases

Answer 17

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

Question 18

collision theory

Answer 18

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

Question 19

homogenous catalyst

Answer 19

is the same physical phase or state as the reactants e.g the destruction of gaseous ozone by chlorine gas

Question 20

heterogenous catalyst

Answer 20

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

Question 21

maxwell boltzmann energy distribution

Answer 21

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.

Question 22

factors that affect the rate of a chemical reaction

Answer 22

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