kinetics I

Question 1

“What conditions are necessary for a reaction to occur between particles?(collision theory)

Answer 1

“1) They must collide in the right direction, facing each other the right way. 2) They must collide with at least a certain minimum amount of kinetic (movement) energy.”

Question 2

“What is the minimum amount of kinetic energy particles need to react called?”

Answer 2

“The activation energy.”

Question 3

“Why do particles need activation energy to react?”

Answer 3

“Particles need activation energy to break the bonds and start the reaction.”

Question 4

“What can be done to help reactions with high activation energies occur?”

Answer 4

“Particles can be given extra energy by heating them.”

Question 5

Why does the Maxwell Boltzmann distribution start at (0, 0)?

Answer 5

Because no molecules have zero energy, so the curve begins at the point where the reactants have no energy.

Question 6

What type of distribution do you get when plotting a graph of the numbers of molecules in a substance with different kinetic energies?

Answer 6

A Maxwell-Boltzmann distribution

Question 7

How does increasing the temperature affect the Maxwell-Boltzmann distribution curve?

Answer 7

Increasing the temperature shifts the curve to the right, as particles, on average, have more kinetic energy and move faster, increasing the proportion of molecules with at least the activation energy to react.

Question 8

How does increasing the temperature affect the frequency of molecular collisions?

Answer 8

Increasing the temperature increases the frequency of molecular collisions, as molecules move faster and collide more often.

Question 9

How does increasing the temperature affect the reaction rate?

Answer 9

Increasing the temperature makes the reaction faster, as the frequency of molecular collisions increases, leading to a higher reaction rate

Question 10

How does increasing the concentration of reactants affect the frequency of collisions in a solution?

Answer 10

Increasing the concentration of reactants increases the number of particles in a given volume of the solution, leading to more frequent collisions between particles

Question 11

Why does increasing the concentration of reactants speed up reactions

Answer 11

Increasing the concentration of reactants provides more chances for collisions to occur, leading to a higher frequency of collisions and thus speeding up the reaction

Question 12

How is increasing pressure similar to increasing the concentration of a solution in terms of speeding up reactions?

Answer 12

Increasing pressure is similar to increasing the concentration of a solution because both result in more particles in a given volume, leading to increased frequency of successful collisions and thus faster reactions.

Question 13

How do catalysts speed up reactions?

Answer 13

Catalysts lower the activation energy by providing an alternative pathway for bonds to be broken and remade, allowing more particles to have enough energy to react

Question 14

How is reaction rate defined?

Answer 14

Reaction rate is the change in the amount of reactant or product per unit time, typically measured in units such as mol dm^-3 s^-1 if the reactants are in solution

Question 15

How can you determine the reaction rate from a graph of reactant or product concentration against time?

Answer 15

The reaction rate is equal to the gradient of the graph, with time on the x-axis

Question 16

How can you determine the rate of reaction at a particular point in a reaction when the points on a graph form a curve?

Answer 16

You can determine the rate of reaction at a particular point by working out the gradient of a tangent to the curve at that point

Question 17

What is the initial rate of reaction?

Answer 17

The gradient at time = 0, which represents the rate of reaction at the beginning of the reaction

Question 18

How can you find the initial rate of a reaction from a concentration-time graph?

Answer 18

You can find the initial rate of a reaction by calculating the gradient of the tangent to the curve at time = 0 on a concentration-time graph

Question 19

What is the formula to calculate the rate of reaction?

Answer 19

Rate of reaction = Amount of reactant used or amount of product formed / Time taken.

Question 20

what is a catalyst

Answer 20

A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy, so a greater proportion of collisions result in a reaction. The catalyst is chemically unchanged at the end of the reaction.

Question 21

What is a notable characteristic of catalysts in reactions?

Answer 21

Catalysts are not consumed in reactions and are remade at the end, allowing a small amount to catalyze a large amount of reactants.

Question 22

How selective are catalysts in the reactions they catalyze?

Answer 22

Catalysts are typically very selective and often only catalyze a single reaction.

Question 23

What is a heterogeneous catalyst?

Answer 23

A heterogeneous catalyst is one that is in a different phase from the reactants, meaning it is in a different physical state. For example, in the Haber Process, gases are passed over a solid iron catalyst.

Question 24

How does increasing the surface area of a heterogeneous catalyst affect the rate of reaction?

Answer 24

ncreasing the surface area of the catalyst increases the number of molecules that can react simultaneously, thus increasing the rate of the reaction.

Question 25

How does a heterogeneous catalyst lower the activation energy of a reaction?

Answer 25

A heterogeneous catalyst works by lowering the activation energy of the reaction, as depicted on a reaction profile diagram.

Question 26

Describe the process by which solid heterogeneous catalysts facilitate reactions.

Answer 26

) Reactant molecules arrive at the surface and bond with the solid catalyst, a process called adsorption. 2) Bonds between the reactant’s atoms weaken and break up, forming radicals—atoms or molecules with unpaired electrons. These radicals combine to form new molecules. 3) The new molecules detach from the catalyst, a process called desorption.”

Question 27

What is a homogeneous catalyst?

Answer 27

A homogeneous catalyst is in the same physical state as the reactants. It is typically an aqueous catalyst for a reaction between two aqueous solutions

Question 28

How does homogeneous catalysis typically occur?

Answer 28

During homogeneous catalysis, the reactants combine with the catalyst to form an intermediate species, which then reacts to form the products and regenerate the catalyst.

Question 29

How does the catalyst affect the activation energy in both homogeneous and heterogeneous catalysis?

Answer 29

How does the catalyst affect the activation energy in both homogeneous and heterogeneous catalysis?

Question 30

What effect does the catalyst have on the rate of reaction?

Answer 30

The catalyst increases the rate of reaction by lowering the activation energy, leading to more particles reacting in a certain amount of time

Question 31

What is the role of iron as a catalyst in ammonia production?

Answer 31

Iron is used as a catalyst in ammonia production to lower the activation energy and increase the rate of the reaction. Without the catalyst, the temperature required for the reaction would be much higher, leading to higher production costs and reduced ammonia yield.

Question 32

How can the use of a catalyst change the properties of a product like poly(ethene)?

Answer 32

Using a catalyst can alter the properties of poly(ethene) to make it more dense, more rigid, and have a higher melting point compared to poly(ethene) made without a catalyst.