kinetics definitions

Question 1

Chemical kinetics

Answer 1

is the study of the rates of chemical reactions and the factors that affect them

Question 2

The rate of chemical reaction

Answer 2

the change in the concentration per unit time

Question 3

What are the factors that affect rate of reaction

Answer 3

the concentration of the reactants involved
temp
physical state of reactants (i.e. powder)
cataylsts
the action of light

Question 4

What is the first order rate constant?

Answer 4

s-1

Question 5

What is the zero order rate constant?

Answer 5

mol L-1 s-1

Question 6

Half life

Answer 6

the time (usually in seconds) for concentration of the reactant to fall to half of its initial value and is denoted by the symbol (t1/2)
e.g. for a 1st order reaction t1⁄2 =ln2/k

Question 7

For a first order reaction does the initial concentration of the reactants change the half life?

Answer 7

No

Question 8

For a second order reaction does the initial concentration of the reactants change the half life?

Answer 8

Yes- half life depends on initial concentration of reactants

Question 9

Collision theory

Answer 9

assumes molecules react by breaking and making bonds; in order to do so molecules must collide in correct orientation and with enough energy above Ea E.G. BIMOLECULAR ELEMENTARY REACTION

Question 10

For an elementary reaction (and ONLY elementary) the order of reaction is

Answer 10

equal to its molecularity

Question 11

Activation energy

Answer 11

amount of energy required to reach the transition state

Question 12

transition state/ activated complex

Answer 12

The transition state in an elementary reaction is the point of highest energy between reactants and products

Question 13

Reactive intermediates

Answer 13

extremely reactive (products that also act as reactants)

Question 14

Reactive intermediates represent

Answer 14

points of minimum energy

Question 15

Transition states represent

Answer 15

points of maximum energy

Question 16

Rate determining step

Answer 16

slowest step

Question 17

Catalysts

Answer 17

substances that speed up chemical reactions without being consumed in the overall process by lowering the activation energy required for the reaction to take place by taking it along an alternative reaction pathway or holding the reactants in the correct configuration to react

Question 18

homogenous catalysts

Answer 18

a catalyst that works in the same phase as the reaction itself (e.g. liquid phase acid catalysis)

Question 19

heterogenous catalysts

Answer 19

a catalyst that works in a different phase as the reaction itself For example: Pt (solid) in the hydrogenation of alkenes (gas).

Question 20

Explosions

Answer 20

reactions whose rates increase dramatically as the reaction proceeds e.g. hydrogen and oxygen gas explosion

Question 21

oscillating reactions

Answer 21

generating products in bursts

Question 22

autocatalytic

Answer 22

reactions that are catalysed by their own products

Question 23

average rate

Answer 23

is the change in rate over time

Question 24

instantaneous rate

Answer 24

is the rate at specific point in time during the course of the reaction

Question 25

rate constant

Answer 25

proportionality constant (k) in rate law
e.g. For a 1st order reaction: rate = k[conc^n]

Question 26

first order reaction

Answer 26

Where the overall reaction order in the rate law is one.

he rate is directly proportional to the concentration of a reactant.