Kinetics

Question 1

When does dynamic equilibrium occur?

Answer 1

When you have a reversible reaction in a close system (nothing can be added to the system or taken away from it, apart from energy )

Question 2

Features of dynamic equilibrium:

Answer 2

• a reversible, chemical reaction is a dynamic process
• Position of equilibrium can be varied by changing certain conditions
• Everything may appear stationary, but if reactions are moving both ways

Question 3

What happens to the quantity at equilibrium?

Answer 3

At Equilibrium the quantities in the mixture stays constant, though the reactions are still continuing. Rates of forward and back reactions are equal.

Question 4

What is homogeneous equilibrium?

Answer 4

When Products and reactants are in the same phase

Question 5

What is heterogeneous equilibrium?

Answer 5

When products and reactants are in more than one phase/different phase

Question 6

What is le Chateliers principal?

Answer 6

When a change is applied to a system in dynamic equilibrium, the system reacts in such a way as to oppose the effect of the change

Question 7

What factors affect the position of equilibrium?

Answer 7

• Concentration
• Pressure
• Temperature

Question 8

How does concentration affect the position of equilibrium?

Answer 8

• A change in the concentration of reactants will also the rate of a forward reaction
• A change in concentration of products will alter the rate of a reverse reaction

Question 9

How can you shift the equilibrium to the right with concentration?

Answer 9

• Increase the concentration of reactants
• Reduce the concentration of product

Question 10

How can you shift the equilibrium to the left with concentration?

Answer 10

• Decrease the concentration of reactants
• Increase the concentration of products

Question 11

What effect does pressure have when moles of gas are equal on both sides?

Answer 11

No change

Question 12

What happens to equilibrium when you increase pressure?

Answer 12

Move to the side with fewer gaseous molecules

Question 13

What happens to equilibrium when you decrease pressure?

Answer 13

Move to the side with more gaseous molecules

Question 14

definition of dynamic equilibrium

Answer 14

a steady state, where the rates of the forward and reverse reaction are the same

Question 15

definition of a steady state

Answer 15

when the conc of the reactants and products remain constant

Question 16

what happens when you increase temp in an exothermic reaction

Answer 16

equilibrium moves to the left

Question 17

what happens when you decrease temp in an exothermic reaction

Answer 17

equilibrium moves to the right

Question 18

what happens when you increase temp in an endothermic reaction

Answer 18

equilibrium moves to the right

Question 19

what happens when you decrease temp in an endothermic reaction

Answer 19

equilibrium moves to the left

Question 20

what effect does catalysts have on equilibrium?

Answer 20

• increases rate of attainment of equilibrium
• does not affect the position of equilibrium
• speed up industrial equilibrium reactions

Question 21

what is the equation for the haber process

Answer 21

N2(g) + 3H2(g) <=> 2NH3(g)
= -92kj/mol

Question 22

what are the conditions for the Haber process and why

Answer 22

• high pressure 2 atmospheres - as very high pressure is expensive and requires special reaction vessels
• low temp 400degrees - rate is highest if its at a high temp

Question 23

the contact process (making sulfuric acid)
equation & conditions?

Answer 23

2SO2(g) + O2(g) <=> 2SO3(g)
= -197KJ/mol

• 450 degrees temp
• low pressure 1 atmosphere

Question 24

Making ethanol

Answer 24

C2H4(g) + H2o(g) <=>CH3CH2OH(g)
= -42

Question 25

what is the formula for the equilibrium law?

Answer 25

aA + bB <=> cC + dD

Question 26

what does the equilibrium law state?

Answer 26

the direction of an equilibrium is dependant on the conc. of components of the reaction

Question 27

equilibrium law equation?

Answer 27

Kc = [C]c [D]d / [A]a [B]b
products / reactants

Question 28

what does K stand for

Answer 28

equilibrium constant

Question 29

what does Kc stand for

Answer 29

equilibrium constant in terms of concentration

Question 30

what does [C] or [D] stand for?
what does [A] or [B] stand for?

Answer 30

• equilibrium conc of the products in mol/dm3
• equilibrium conc of the reactants in mol/dm3

Question 31

what power is each conc raised to in a Kc equation

Answer 31

each conc is raised to the power of its balancing number in the overall equation

Question 32

units for Kc

Answer 32

change depending on the balancing number

Question 33

what does the equilibrium constant in terms of conc (Kc) compare?

Answer 33

the conc of reactants and products present at equilibrium ‘how far’ the equilibrium has shifted

Question 34

what does a large Kc value mean?

Answer 34

the equilibrium position lies to the right hand side of the reaction and favours the product

Question 35

what does a low Kc value mean?

Answer 35

the equilibrium position lies to the left hand side of the reaction and favours the reactants

Question 36

what is a ‘central equilibrium’?

Answer 36

(equal con of reactant and products) has Kc = 1

Question 37

what is the only factor that effects Kc?

Answer 37

temperature
Kc is only constant at a constant temperature

Question 38

what would an equation have no units

Answer 38

no units, as they cancel out. this is due to there being an equal number of moles on both sides of the equation