Topic 16 Kinetics II Flashcards
What is the unit for rate of reaction? Usually
moldm-3s-1
What is the definition of rate of reaction?
Change in measurable quantity over time (s)
What is the rate constant?
k
What is the definition of half life?
Time taken for concentration of a reactant to half
It is a first order reaction
What is the activation energy used for?
Breaking bonds
What is a rate limiting step?
the slowest step in chemical reactions, which determines the overall rate of the other reactions in the pathway
What is a zeroth order reaction?
Change in concentration with no change in rate
What is a first order reaction?
Change in conc is proportional to change in rate
E.g. double conc = double rate
What is a second order reaction?
Change in conc = (change in rate )^2
Double the conc, quadruple the rate
How to find overall order of a reaction?
Find rate equation
E.g. k[x][y][z]^2
Add them up = 4 overall order
What is the Arrhenius Equation?
Finding activation energy (Ea) using
- temp T (K)
- rate constant k (s-1)
Find gradient (m) where x axis: 1/T, y axis: ln k
m should be negative
m x -8.31 %1000
Ans should be positive (kJ mol-1)
What does a mop do?
E.g. in CP13
Thiosulfste (mop) reacts with Iodine (product of reaction we study, reactant twitch mop) as it forms
You time how long it takes for a certain SAME mole of iodine is formed
Same amount of mop added, change other concs
What is the purpose of a mop?
Makes reaction measurable
Thiosulfate eeacts with I2 as it forms so
So solution doesn’t turn blue-black immediately
When all thiosulfate is used up, solution turns blue black
To time how long it takes to make a certain number of moles of I2
What is SN1 and its’ rate equation?
1st order Nucleophilic substitution
rate = k[halogenoalkane]
Is SN1 or SN2 faster?
SN2 because it’s 2nd order
