AC2: Reaction Kinetics II

Question 1

What order is A if the concentration doubles and the rate also doubles

Answer 1

First order

Question 2

What order is A if the concentration doubles but the rate quadruples

Answer 2

Second order

Question 3

When the equation is Rate=[A][B], what is the overall order, and what is the order for A and what is the order for B

Answer 3

Second order overall since A and B are both first order (1+1=2). First order in concentration of A and first order for concentration of B

Question 4

What is the rate equation, involving A & B, if the overall order was 4 and the order of A was second

Answer 4

Rate=k[A]^2[B]^2
Both are second order since 2+2=4

Question 5

When solving k what is always the most important thing to remember

Answer 5

The unit

Question 6

What would happen to the rate if [A] was tripled
Rate=k[A]^2

Answer 6

Rate increases x9

Question 7

What would happen to the rate if both A and B were doubled
Rate=k[A][B]^2

Answer 7

If A doubles the rate doubles, x2, and if B doubles the rate quadruples, x4, so rate increases by a factor of 8

Question 8

What is the name of the slow step in chemical reactions

Answer 8

Rate determining step

Question 9

What are the 2 rules of stepwise mechanisms

Answer 9

• The rate equation only includes reacting species involved in the rate determining step
• The orders in the rate equation match the number of species involved in the RDS

Question 10

A->B->C reaction, what is the name of B, something that is created and destroyed in the reaction

Answer 10

Intermediate

Question 11

When creating your own mechanism, what is the final step to do to check it’s the same as the chemical equation

Answer 11

Add up the LHS and add up the RHS

Question 12

What is the name of a reactant that isn’t used up in the chemical equation but is regenerated in the final step of the mechanism

Answer 12

Catalyst

Question 13

Explain what happens to the rate of reaction when the temperature increases (5 marks)

Answer 13

• Draw Boltzmann distribution curve
• Draw a second line on the curve to show the hotter temperature
• Higher proportion of particles with energy above the activation energy

Question 14

In the Arrhenius equation, what does the k stand for

Answer 14

Rate constant

Question 15

In the Arrhenius equation, what does the A stand for

Answer 15

Pre-exponential factor

Question 16

In the Arrhenius equation, what does the Ea stand for

Answer 16

Activation energy

Question 17

In the Arrhenius equation, what does the R stand for

Answer 17

Gas constant

Question 18

In the Arrhenius equation, what does the T stand for and what are the units

Answer 18

Temperature and Kelvin units

Question 19

if the temperature raises by 10 degrees, by what factor does the rate constant roughly increase by

Answer 19

2 / it roughly doubles

Question 20

Using the Arrhenius equation, but the lnk=version, what part of the given equation in, the formula sheet is equal to the y in y=mx+c

Answer 20

the lnk

Question 21

Using the Arrhenius equation, in the form lnk= what part equals the m in y=mx+c

Answer 21

the -Ea/ R

Question 22

Using the Arrhenius equation, in the form lnk=, what part equals the x in y=mx+c

Answer 22

the 1/T

Question 23

Using the Arrhenius equation in the form lnk=, what part equals the c in y=mx+c

Answer 23

lnA

Question 24

When reading info from an Arrhenius plot, what is equation to the gradient

Answer 24

-Ea/R

Question 25

When reading info off the Arrhenius plot, what is the unit straight off the graph for Ea

Answer 25

Jmol ^-1 / joules per mole

Question 26

How do you convert joules per mole to kJ per mole

Answer 26

divide by 1000

Question 27

What is the crucial thing to remember when calculating the gradient from an Arrhenius plot, to do with the actual x / y values

Answer 27

Check to see if the values are x10^of something. Then before calculating the gradient make sure you include the factor of 10 it might be

Question 28

After plotting an Arrhenius plot, what is the next thing to do in order to calculate the gradient

Answer 28

Draw line of best fit

Question 29

What does the A, in the Arrhenius equation demonstrate

Answer 29

The orientation of the particles colliding

Question 30

How do you find A from the Arrhenius plot

Answer 30

The y intercept =lnA
Then do e to the power of the intercept to find A

Question 31

What is the unit of A

Answer 31

The same as the unit for k

Question 32

Why is the unit for A the same as the unit for k

Answer 32

Because the Arrhenius equation is k=Ae^-Ea/RT, and the e^-Ea/RT is unitless- leaving k=A for the units

Question 33

Is the Ea for a reaction involving iodocyclopentane higher or lower than the Ea for a reaction involving chlorocyclopentane

Answer 33

Ea is lower for the reaction with iodocyclopentane since the C-I bond is weaker than the C-Cl bond therefore less energy is required to overcome the bond

Question 34

Weak answer: Alkenes react via electrophilic substitution , what is the improved/ corrected answer

Answer 34

Alkenes react via electrophilic addition

Question 35

Weak answer: Pentan-2-ol undergoes elimination to form pent-1-ene and pent-2-ene

Answer 35

Isomers of pent-2-ene E/Z