Equilibrium

Question 1

What does reversible mean?

Answer 1

Reaction which goes in both forward and backward directions.

Question 2

What does dynamic (equilibria) mean?

Answer 2

Rate of forward reaction equal to rate of backward reaction and amounts of reactant or product remains constant.

Question 3

What does reaction rate mean?

Answer 3

Change of concentration (amount) of reactant or product with respect to time.

Question 4

What does activation energy mean?

Answer 4

Minimum amount of energy required for reaction to occur.

Question 5

What does homogeneous mean?

Answer 5

Reaction in which all reactants and products are in same physical state.

Question 6

What does heterogenous mean?

Answer 6

Reaction in which all reactants and products are not in same physical state.

Question 7

What is a homogeneous catalyst?

Answer 7

Reaction in which catalyst and reactants and products are in same physical state.

Question 8

What is a heterogenous catalyst?

Answer 8

Reaction in which catalyst is in different state to reactants and products.

Question 9

What is Le Chatelier’s Principle?

Answer 9

If dynamic equilibrium is disturbed by changing conditions, position of equilibrium moves to counteract change.

Question 10

Why conditions must be met for dynamic equilibrium?

Answer 10

System must be closed.

Equilibrium must be approachable from both directions.

At equilibrium properties such as mass, volume, conc, pressure and colour remain unchanged if temp is constant.

At equilibrium particles continue to react in both directions.

Question 11

What factors can affect dynamic equilibrium?

Answer 11

Concentration
Temperature
Pressure

Question 12

What happens to equilibrium when the concentration of one of the reactants increases?

Answer 12

Equilibrium will move so conc of reactant decreases, moves to right.

Question 13

What happens to equilibrium when the concentration of one of the reactants decreases?

Answer 13

Equilibrium moves so conc of reactant increases, moves to left.

Question 14

What happens to the equilibrium when a catalyst is added to a reaction?

Answer 14

Increases rate of reaction at which equilibrium established.

Does not affect composition of equilibrium mixture as rate if forward and reverse reaction increase by equal amount.

Question 15

What happens to equilibrium when the pressure of one of the reactants increases?

Answer 15

Equilibrium moves to side with fewer moles of gas to decrease pressure of reactant, moves to right.

Question 16

What happens to equilibrium when the pressure of one of the reactants decreases?

Answer 16

Equilibrium moves to left where fewer moles of gas to increases pressure of reactant.

Question 17

What happens to equilibrium when the temperature of one of the reactants increases?

Answer 17

Equilibrium moves to side where reaction is endothermic and increases rate if reaction to decrease temp.

Question 18

What happens to equilibrium when the temperature of one of the reactants decreases?

Answer 18

Equilibrium moves to side of exothermic reaction and increases rate of reaction to increase temp.

Question 19

What is the symbol equation for the Haber process?

Answer 19

3H2 (g) + N2 (g) > 2NH3 (g)

Question 20

What is the enthalpy change of the Haber process?

Answer 20

-92kJ mol^-1

Question 21

What are the conditions required for the Haber process, with reasons?

Answer 21

200-250 atm - compromise chosen on economic grounds.

400-450oC - lower temp, slower rate of reaction for acceptable yield.

Iron catalyst - speeds up rate.

Question 22

How can the productivity of the Haber process be maximised?

Answer 22

Iron catalyst speed up both reaction directions, without affecting equilibrium.

Un reacted N2 and H2 recycled and reacted again.

Question 23

What are the 3 stages involved in the contact process for the manufacturing of sulfuric acid?

Answer 23

1. Production of sulfur dioixde, SO2
2. Production of sulfur trioxide, SO3
3. Absorption of sulfur trioxide

Question 24

What is the involved in the first stage of the contact process for the manufacturing of sulfuric acid?

Answer 24

Liquid sulfur sprayed into combustion chamber with excess dry air, gases come out at 1,300oC and cooled.

Question 25

What is the involved in the second stage of the contact process for the manufacturing of sulfuric acid?

Answer 25

Sulfur dioxide and excess air passed over vanadium (V) oxide catalyst at 425oC and 2 atm.

Question 26

What is the involved in the third stage of the contact process for the manufacturing of sulfuric acid?

Answer 26

Sulfur dioxide cannot absorbed directly into water so instead absorbed by water in 98% sulfuric acid.

Question 27

What are the equations for each stage of the contact process for manufacturing sulfuric acid?

Answer 27

1. S (s) + O2 (g) > SO2 (g) 2. 2SO2 (g) + O2 (g) > 2SO3 (g) 3. SO3 (g) + H2O (l) + H2SO4 (aq) > 2H2SO4 (aq)

Question 28

What are the conditions for the contact process for manufacturing sulfuric acid?

Answer 28

Pressure - 1 atm Catalyst - vanadium (V) oxide Temperature - 400-450oC

Question 29

How does temperature affect the yield of a reaction?

Answer 29

Lower temp increases yield, but reaction much slower.

Question 30

What are the equations used to calculate the equilibrium constant Kc in homogenous equilibria?

Answer 30

aA + bB > cC + dD Kc = [C]^c [D]^d / [A]^a [B]^b

Question 31

What is equilibrium constants, Kc?

Answer 31

Numerical value which indicates how far equilibrium is over to right hand side.

Question 32

What happens if Kc > 1?

Answer 32

Large proportion of product than reactants in equilibrium mixture.

Question 33

What happens if Kc < 1?

Answer 33

Larger proportion of reactants than products in equilibrium mixture.

Question 34

When is Kc constant?

Answer 34

At particular temp.

Question 35

What do the square brackets show in the equation Kc = [C]^c [D]^d / [A]^a [B]^b?

Answer 35

Concentrations in mol dm^-3

Question 36

What are the indices in the equation Kc = [C]^c [D]^d / [A]^a [B]^b?

Answer 36

Numbers in front of each substance in equation.