Kinetics I- Y12/13

Created by

Yassin

Cards (43)

What is collision theory?
For particles to react they must collide in the correct orientation and with sufficient energy to break the bonds in the reactants
What 5 factors can affect the rate of reaction?
temperature
surface area
concentration
pressure
catalyst
Define activation energy?
minimum energy needed to break the bonds to start a reaction
What symbol represents activation energy?
Ea
What is the name for the species that exists at the top of the curve of an enthalpy diagram?
activated complex
What is another name for the activated complex?
transition state
What 2 things does the activated complex have?
extra energy and unstable
Why does the activated complex have extra energy and is unstable?
some bonds are in the process of being made and some bonds are in the process of being broken
What are the 3 things to note in a normal Maxwell-Boltzmann distribution graph? 
no particles have 0 energy
most particles have an intermediate energy around the peak
very few particles have high energies
What does the area under a Maxwell Boltzmann distribution show?
number of particles
What goes on the x axis in a Maxwell-Boltzmann Distribution graph?
Energy
What goes on the y axis in a Maxwell-Boltzmann Distribution graph?
fraction of particles with energy
What is labelled at the peak of a Maxwell-Boltzmann Distribution graph?
most probable energy Emp
What is labelled beside the peak in a Maxwell-Boltzmann Distribution graph?
average energy
When lowering temperature what happens to the shape of a Maxwell Boltzmann graph?
peak shifts to the left and is higher
When lowering temperature what happens to the number of particles with energy greater than the activation energy?
decreases
What is the effect of a catalyst on the shape of a Maxwell Boltzmann graph?
none
With the presence of a catalyst what happens to the number of particles with an energy greater than the activation energy?
increases
Why does the Maxwell-Boltzmann distribution curve start at the origin?
there are no molecules with no energy
Explain the process that causes some molecules in the sample to have very low energies?
collisions cause some molecules to slow down
What are catalysts?
substances that increase rate of reaction by providing an alternative reaction pathway without being used up
What is adsorption in a catalyst?
reactant forms weak bonds with metal atoms of catalyst
What is desorption in a catalyst?
products break away from metal atoms
Why are the metals used in a catalytic converter powdered?
large surface area from a small amount which reduces cost
Why is the strength of the bonds holding reactant on surface of catalyst critical?
must be strong enough to hold reactants for long enough to react but must be weak enough to release product easily
What is the name for a catalyst that is in a different phase than a reactant?
heterogeneous
What is the name for a catalyst that is in the same phase as a reactant?
homogeneous
What is the slow step of a reaction also known as?
Rate determining step
In a rate equation what does k mean?
rate constant
What factors increase the rate constant?
Temperature
catalyst
In a rate equation what does the superscript numbers mean?
orders of reaction
What effect does an order of 0 have on rate?
no effect
What 2 metals are used as a catalyst in catalytic converters?
palladium and rhodium
What experimental method is used to measure the change in concentration?
titration
How to convert from degrees celsius to Kelvin?
add 273
What is the formula for the straight line ( in terms of the Arrenhius Equation)?
ln(k)= -Ea/R x 1/T + ln(A)
Why is sodium thiosulfate added in the iodine clock reaction?
allows iodine and starch to react together quickly
Why is starch added in the iodine clock reaction?
reacts with iodine and turns solution to blue/black
Why is the volume of water changed in the iodine clock reaction each time?
change the concentration of KI and keep overall volume the same
Why is a water bath used in the iodine clock reaction?
Temperature control