Kinetics

Question 1

What are the 3 conditions needed for a reaction to occur

Answer 1

• particles must collide in the correct orientation
• particles must collide with sufficient energy
• particles must collide

Question 2

Factors that affect the rate of reaction

Answer 2

• temperature
• surface area
• concentration
• pressure

Question 3

What are the different techniques used to measure rates of reactions

Answer 3

• change of colour (calorimetry)
• change in mass (scale)
• change in volume (gas syringe)
• change in concentration (titration)

Question 4

Why does the rate of reaction decrease over time

Answer 4

the concentration of reactants decreases, thus the frequency of collisions decreases as well

Question 5

Define activation energy

Answer 5

the minimum amount of energy needed for a reaction to occur

Question 6

The effect of a catalyst on the activation energy

Answer 6

it provides the reactants with an alternative pathway which has a lower activation energy

Question 7

The effect of increasing temperature on Maxwell-Boltzmann curve

Answer 7

more particles gain sufficient energy due to the increase in kinetic energy – more frequent and successful collisions
- the curve flattens and moves to the right

Question 8

How to find the rate of a reaction at a specific time

Answer 8

draw a tangent line at the point
- calculate the gradient

Question 9

How to find the average/overall rate of reaction using a graph

Answer 9

take max and min points
- calculate the gradient

Question 10

How to find the order of a reaction

Answer 10

k [A]m [B]n
A= concentration
K= rate constant
m= order of the reaction

Question 11

What does a reaction with order 0 mean + units

Answer 11

changing the concentration doesn’t have any effect on the rate of reaction
mol dm-3 s-1

Question 12

What does a reaction with order 1 mean + units

Answer 12

changes in the concentration of reactants is directly proportional to the changes in the rate of reaction
s-1

Question 13

What does a reaction with order 2 mean + units

Answer 13

changes in the concentration of reactants leads to an increase in the rate of reaction equal to the square of the change
mol-1 dm3 s-1

Question 14

what is special about the rate constant

Answer 14

it is temperature dependent
- increasing the temperature will increase the value of the rate constant

Question 15

What are the graphs for order 0, 1 and 2
concentration vs time

Answer 15

order 0: linear negative
order 1: negative exponential
order 2: even more negative exponential (steeper)

Question 16

What are the graphs for order 0, 1 and 2
rate vs time

Answer 16

order 0: straight horizontal line
order 1: linear positive gradient
order 2: positive exponential

Question 17

What is the rate determining step

Answer 17

the slowest step of the equation

Question 18

What are the 2 types of catalysts

Answer 18

homogeneous: catalysts is in the same phase as the reactants
heterogeneous: catalysts is in a different phase as the reactants

Question 19

Characteristics of the rate determining step

Answer 19

• It has the highest activation energy
• the rate equation tells which one is the RDS
• the rate equation shows the reactants of the RDS

Question 20

What is the Arrhenius equation

Answer 20

k = Ae ^-Ea/RT
k = rate constant
A = Arrhenius constant
R = gas constant
T = temperature

Question 21

Another Arrhenius equation

Answer 21

lnk = lnA - Ea/RT
y = c -mx

Question 22

Outline how surface area affects the rate of a reaction

Answer 22

greater surface area, more frequent and successful collisions, greater rate of reaction