9-16. Kinetics I and II Flashcards
What is an isomer
Same molecular formula but atoms are arranged differently
What is a structural isomers
Different structural arrangements
What is a chain isomer and it’s properties
The carbon skeleton is arranged differently (straight and branched)
Similar chemical properties
Different physical properties
What is a positional isomer and it’s properties
The skeleton and functional group are the same but the functional group is attached to a different carbon atom
Different chemical and physical properties
What is a functional group isomer and it’s properties
The same atoms can be arranged into different functional groups
Very different chemical and physical properties
What bonds can atoms rotate around
Single carbon bonds
What bonds don’t rotate
Carbon double bonds
What does planar mean
All atoms lie in the same plane
What is stereoisomerism
Same structural formulae but a different arrangement
What is an E-Isomer
Has the same group positioned across the double bond
What is a Z-Isomer
Has the same groups either both above or below the double bond
What is collision theory
Particles must collide to react in the right direction and collide with at least a certain minimum amount of kinetic energy
What is activation energy
Minimum amount of energy the reactants must have for a reaction to happen
What happens when you increase the concentration of reactants
There is more particles so they collide more frequently which increases the rate of reaction
What happens if you increase the pressure
There are more particles in a given volume which increases the frequency of collisions
What does a catalyst do
Lowers the activation energy by providing a different way for bonds to be broken which allows more particles to have enough energy to react
What happens when you increase the temperature of a reaction
More particles have the minimum activation energy and will move faster.
What is the definition of rate of reaction
The change in amount of reactants or product per unit of time
What is initial rate
The rate at the start of a reaction
What is a catalyst
Increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy so a greater proportion of collisions result in a reaction.
Economic benefits of catalysts
Lower production costs, give more products in a shorter time
Using catalysts can change properties
What’s a heterogenous catalyst
Catalyst in a different physical state from reactants
The reaction happens on the surface of a heterogeneous catalyst so increasing the surface area increases the rate of reaction
What’s a homogenous catalyst
A catalyst in the same physical state as the reactants
During this the catalyst combine with the reactants to make an intermediate species which react to form products and reform the catalyst
Ways to follow rates of reaction
Gas volum
Loss of gas
Change in pH
Colour change
Titration
Electrical conductivity
What is 0 order reaction
If concentration of X changes and the rate stays the same the order of reaction with respect to X is 0
What is 1st order reaction
If the rate is proportional to the concentration of X then the order with respect to X is 1
What is 2nd order reaction
If the rate is proportional to the concentration of X^2 then the order of reaction with respect to X is 2
What is Half life
The time it takes for half of the reactant to be used up
How to work out the half life of a reaction
Work out the half life by drawing a concentration time graph. Draw lines scores from the Y- axis at points where the concentration has halved and read off the time taken
Rate equation
Rate = k (A)^m(B)^n
What is K
Rate constant
Bigger it is the faster the reaction
What is the rate determining step
The slowest step in a multi step reaction mechanism.
The overall rate is decided by the rate determining step
What is nucleophilic substitution
When a nucleophile attacks another molecule and is swapped for one of the attached groups.
What type of mechanism for nucleophilic substitution for primary and secondary halogenoalkanes
Sn2
What time of nucleophilic substitution mechanism is secondary and tertiary halogenoalkanes
Sn1
What is the Arrhenius equation and what do the symbols mean
k = Ae ^Ea/RT
k= rate constant
A = frequency of collisions constant
e = constant e
-Ea = - activation energy
R = gas constant 8.31
T = temperature in Kelvin
Arrhenius constant in logarithmic form
ln k = ln A - Ea/RT
What is the graph of an Arrhenius plot
ln k against 1/T
What is an optical isomer
Molecules that are mirror images of each other
What is a chiral centre
A carbon atom that has four different groups attached to it
Properties of optical isomers
2 enantiomers
Can’t be superimposed
Rotate plane polarised light
What is a racemic mixture
Contains equal quantities of each negations of a chiral compound. Don’t rotate plane polarised light as they cancel.
