Kinetics

Question 1

Rate

Answer 1

Difference in concentration over a given time

Question 2

Half life

Answer 2

Time taken for concentration of reactant to half

Question 3

Distinction between first and second order

Answer 3

2nd order slows down more rapidly than 1st order and for second order half life decreases as concentration decreases

Question 4

Zero order

Answer 4

Plot [A] against t, half life decreases as [A] decreases

Question 5

Multiple reactants

Answer 5

Rate law is additive eg two first order reactants gives second order overall

Question 6

Isolated method

Answer 6

Way of measuring rate, arrange all concentrations in excess except one, excess concs reman ~ constant

Question 7

Elementary reactions

Answer 7

Single step at molecular level, rate law determines by single probability and order = molecularity eg uni molecular

Question 8

Unimolecular reaction

Answer 8

Elementary first order reactions of type A -> products, every A behaves independently so rate proportional to no of A molecules

Question 9

Bimolecular reactons

Answer 9

Rate proportional to no of pairs of reactants

Question 10

Rate determining step

Answer 10

Overall rate = rate of slowest sep

Question 11

Rapid pre-equilibrium

Answer 11

Concs of some species remain in balance

Question 12

Organic chemists rule of thumb

Answer 12

Rate of typical reaction doubles for every 10C increase around room temp

Question 13

What does a larger value of Ea mean

Answer 13

K more sensitive to T

Question 14

What’s the need for A in Arrhenius equation

Answer 14

Accounts for all factors that affect rate other than energy

Question 15

Catalysts

Answer 15

Provide alternative route by decreasing activation energy

Question 16

Counting rate of collisions

Answer 16

Collisions occur when impact parameter, b < ra+rb, has area = collision cross section, rate proportional to collision cross section, average relative speed of molecule and number density of molecules

Question 17

What’s required for successful collisions

Answer 17

Do molecules collide with enough energy and do they collide n correct geometry

Question 18

Transition state theory

Answer 18

Rate proportional to concentration of transition state ie chance of forming transition state

Question 19

K++

Answer 19

Pseudo equilibrium constant for transition state, [AB++]/[A][B]