Kinetics and Equilibrium

Question 1

What is the collision theory?

Answer 1

Reactions can only occur when collisions take place between particles when they have sufficient energy.

Question 2

Define activation energy.

Answer 2

The minimum energy needed for particles to collide to start a reaction

Question 3

What does the Maxwell Boltzmann distribution show?

Answer 3

The spread of energies that molecules of a gas have at a particular temperature

Question 4

Why should the energy distribution go through the origin on the graph?

Answer 4

There are no molecules with no energy.

Question 5

How does the Maxwell Boltzmann distribution graph change if the temperature is increased?

Answer 5

Shifts to the right and down

Question 6

How does adding a catalyst affect the Maxwell - Boltzmann distribution graph?

Answer 6

The graph stays the same but there are more particles with the activation energy or above

Question 7

What does reducing the volume of the container do to the graph?

Answer 7

The graph stays the same and there is the same number of particles with the activation energy. ( no effect )

Question 8

What does removing half the molecules do to the Maxwell-Boltzmann curve?

Answer 8

The curve is shifted down and there is less particles with the activation energy

Question 9

What does reducing the temperature do to the Maxwell Boltzmann distribution curve?

Answer 9

The curve is shifted to the left and up and there is less particles with the activation energy

Question 10

What does adding an inert gas do to the Maxwell Boltzmann distribution graph?

Answer 10

The graph stays the same and the number of particles with the activation energy also stays the same

Question 11

What is an equation for rate?

Answer 11

1/t

Question 12

What is the effect on the rate when pressure and concentration is increased?

Answer 12

• More particles are in a given volume
• Successful collision are more frequent
• Therefore the rate of reaction increases

Question 13

What is the effect on the rate when temperature is increased?

Answer 13

• There is an increase in the number of molecules with activation energy
• More successful collisions in a given time or ( higher frequency of successful collisions)

Question 14

What is the effect on the rate when a catalyst is added?

Answer 14

• Provides a different pathway
• with lower activation energy

Question 15

Describe the characteristics of Dynamic equilibrium.

Answer 15

• Rate of forward reaction = Rate of backwards reaction
• Closed system
• Concentrations of reactants and products remain the constant
• Dynamic reactions occur at the same time

Question 16

What is the definition of Le Chatelier’s Principle?

Answer 16

• If a system at equilibrium is changed the equilibrium moves in the direction to oppose the change.

Question 17

Eg. Co(H20)6 + 4Cl –> CoCl4 + H2O ( effect of concentration)
What will happen if I add Cl?

Answer 17

• The equilibrium moves to remove the Cl, producing more CoCl4 and H20 and turns blue

Question 18

2NO2 —> N2O4 ( effect of pressure)
What will happen if the pressure is increased?

Answer 18

• The equilibrium would shift to the side with fewer moles
• Producing more N2O4
• Turning the mixture colourless

Question 19

A + B —> C + D ( forward reaction is exothermic )
What will happen if the temperature was raised?

Answer 19

• The equilibrium moves to cool down by moving in the endothermic direction, producing more A and B

Question 20

What is the effect of adding a catalyst on the equilibrium?

Answer 20

• Catalysts don’t shift an equilibrium one way or another, they just increase the rate of attainment of equilibrium ( they speed up the forward and reverse reactions )

Question 21

What is the equation for the Haber process?

Answer 21

N2 (g) + 3H2 (g) ⇌ 2NH3 (g) ( forward reaction is exothermic )

Question 22

What are the conditions for the Haber process?

Answer 22

400°C-450°C
200atm
Iron catalyst

Question 23

What are the uses of ammonia?

Answer 23

• Used as a fertiliser, explosives, drugs, dyes and nylon

Question 24

What should we consider as well as yield during a reaction?

Answer 24

• Cost of building or machinery
• Temperature and pressure costs
• Rate of reaction

Question 25

What is the equation for the hydration of ethene?

Answer 25

C2H4(g) + H2O(g) → C2H5OH(l)

Question 26

What are the conditions for the hydration of ethene?

Answer 26

300°C 60-70 atm concentrated H3PO4 catalyst

Question 27

What is the equation for fermentation of glucose?

Answer 27

C6H12O6 (aq) ----> 2C2H5OH (aq) + 2CO2 (g)

Question 28

What are the conditions for fermentation?

Answer 28

35°C No oxygen yeast catalyst

Question 29

What are the main uses of ethanol?

Answer 29

- Solvent in cosmetics, fuel, alcohol, drugs and detergents

Question 30

What is the equation for the production of methanol?

Answer 30

CO(g) + 2H2 (g) ⇌ CH3OH (g)

Question 31

What are the conditions for the production of methanol?

Answer 31

-220 °C - 100 atm - Catalyst made of Copper, Zinc Oxide and Alumina

Question 32

What are the uses of methanol?

Answer 32

Fuel mixtures, chemical feedstock and can be oxidised into methanal Methanal is used to make glues, paints and plastics

Question 33

What are the characteristics of dynamic equilibrium?

Answer 33

- The rate of forward reaction is equal to the rate of the backward reaction

Question 34

What is the definition of Kc (equilibrium constant)?

Answer 34

The equilibrium constant is a value that describes the position of equilibrium for a reaction at a given temperature

Question 35

How is Kc calculated?

Answer 35

From the equilibrium concentrations of the reactants and the products

Question 36

What does the "c" in Kc show?

Answer 36

It shows that the value has been calculated by using equilibrium concentrations in mol/dm3

Question 37

What are the steps in calculating Kc?

Answer 37

1. aA + bB ---> cC + dD Kc= [ C ]^c [ D ]^d / [ A ]^a [ B ]^b ( products over reactants) 2. Add mol/dm^3 to work out the units 3. Eg. CH3OH --- CO + 2H2 Initial: 10 0 0 Changes: -2 2 4 Eqm: 8 2 4 Moles can be converted into concentration using conc=mol/vol 4. Add all values to products over reactants make sure you divide by volume!

Question 38

What predominates if Kc is much greater than 1?

Answer 38

The products predominate ( most abundant) over the reactants so the eqm is to the right

Question 39

What predominates if Kc is much less than 1?

Answer 39

The reactants predominate (most abundant) over the products so the eqm is to the left

Question 40

What does Kc have to be greater than for the reaction to go to completion?

Answer 40

10^10

Question 41

What does Kc have to be less than to not go to completion?

Answer 41

10^-10

Question 42

What are the factors effecting Kc?

Answer 42

- Concentration - Catalysts - Temperature

Question 43

State and explain whether concentration effects Kc.

Answer 43

- Kc is not effected by concentration because the position of equilibrium will shift to restore the concentrations to the original values.

Question 44

State and explain whether catalysts effect Kc.

Answer 44

- No effects as catalysts only increase the rate of the forward and backward reactions equally

Question 45

Does temperature effect Kc? Draw the table that is used to work it out.

Answer 45

- Yes Reaction : Temp change : Direction of eqm : Effect on p / r : Effect Kc