Equilibria 6

Question 1

dynamic equilibrium

Answer 1

• closed container
• either direction
• rates happen at the same time

Question 2

la chandeliers principle

Answer 2

if a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance

Question 3

change in concentration

Answer 3

• increase the concentration of the reactant creates more products so the equilibrium moves to the right
• increase the concentration of the product = equilibrium shifts to the left
• decreasing the pressure has the opposite effect

Question 4

change in pressure

Answer 4

• only with gases

- increasing the pressure shifts the equilibrium to the side with fewer gas molecules

Question 5

change in temperature

Answer 5

• increasing the temperature (adding heat) shifts to the endothermic direction to absorb the heat
• decreasing the heat shifts in the exothermic direction to produce more heat
• one direction would be exothermic and then other would be endothermic

Question 6

change in conditions with a catalyst

Answer 6

they don’t effect on the position of equilibrium but allow equilibrium to happen quicker

Question 7

Ammonia

Haber process

Answer 7

• iron catalyst
• used to make fertiliser
• Air (nitrogen)
• methane (natural gas)

N2 + 3H2 — 2NH3 -92kJmol-1

-200 atm and 670K

Question 8

Ethanol

Answer 8

• fermentation or hydration
• used in drugs, detergents, inks and motor fuel
• high pressure (equilibrium moves to the right) = causes ethene to polymerise and increases the costs
• low temperature (equilibrium moves to the right) = reduce the rate of reaction

Question 9

Methanol

Answer 9

• chemical feedstock
• methanal = bakelite
• highest yield at low temperature and high pressure
• 500K and 10000kPa

Question 10

equilibrium constant

Answer 10

• different in different reactions

- doesn’t change unless the temperature changes

Question 11

effect of changing the temperature on the equilibrium constant

endothermic (decrease in temperature)

Answer 11

kc decrease
effect on products decrease
effect on reactants increase
equilibrium moves to the left

Question 12

effect of changing the temperature on the equilibrium constant

endothermic (increase in temperature)

Answer 12

kc increase
effect on products increase
effect on reactants decrease
equilibrium moves to the right

Question 13

effect of changing the temperature on the equilibrium constant

exothermic (decrease in temperature)

Answer 13

kc increase
effect on products increase
effect on reactants decrease
equilibrium moves to the right

Question 14

effect of changing the temperature on the equilibrium constant

exothermic (increase in temperature)

Answer 14

kc decrease
effect on products decrease
effect on reactants increase
equilibrium moves to the left

Question 15

effect of changing the concentration on the equilibrium constant

Answer 15

doesn’t change

Question 16

catalyst and equilibrium constant

Answer 16

catalysts have no effect, affects the rates of forwards and backwards reaction

Question 17

What does a closed system mean?

Answer 17

Nothing can enter or lose

Question 18

What does a negative 🔺H mean?

Answer 18

Forward reaction is exothermic

Question 19

Methanol
CO2 + 3H2 ↔️ CH3OH + H2O 🔺H=-49 KJmol-1

Temperature decrease

Answer 19

Yield CH3OH increases
Forward reaction is exothermic therefore equilibrium shifts to the right
Oppose the decrease in temperature

Question 20

Methanol
CO2 + 3H2 ↔️ CH3OH + H2O 🔺H=-49 KJmol-1

Increase pressure

Answer 20

Yield of CH3OH increases

More molecules on the left therefore equilibrium shifts right to oppose the increase in pressure

Question 21

Methanol
CO2 + 3H2 ↔️ CH3OH + H2O 🔺H=-49 KJmol-1

Catalyst added

Answer 21

Speeds both reaction equally

Equilibrium would be reached faster

Question 22

Haber process

Answer 22

CH4 + 3H2 ➡️ CO + 3H2 ( reaction needed to get hydrogen)

Raw materials - air ( nitrogen ) - water - natural gas
N2 + 3H2 ↔️ 2NH3
Iron catalyst
Uses of ammonia - fertiliser - nylon - explosives
High pressure - increase yield / more moles on the left hand side / equilibrium shifts to the right
Low temperature - higher yield / forward reaction exothermic / equilibrium shifts to the right

Question 23

Ethanol

Fermentation

Answer 23

C6H12O6 ➡️ 2C2H5OH + 2CO2

Question 24

Ethanol

Stream

Answer 24

C2H4 + H2O ↔️ C2H5OH

Exothermic
Lower temperature = increase yield
300 degrees and 60-70 atmospheres
Phosphoric acid catalyst

Question 25

Methanol

Answer 25

50-100 atmospheres
250 degrees

2H2 + CO ↔️ CH3OH

Question 26

Production of lime

Answer 26

CaCO3 ↔️ CaO + CO2
Forwards reaction is endothermic
1000 degrees in the lime limekiln
Batch process

Question 27

Contact process reactor

Answer 27

Sulphur dioxide mixed with air ( ratio 2:1)
Catalyst of vanadium
450 degrees
1-2 atmospheres of pressure
Exothermic

2SO2 + O2 ↔️ 2SO3

Question 28

Homogeneous

Answer 28

All reactants and products are in the same phase

Question 29

reversible reaction

Answer 29

forward and reverse reactions proceed at equal rates

the concentrations of reactants and products remain constant

Question 30

Kc

Answer 30

deduced from the equation for a reversible reaction

The concentration, in mol dm–3, of a species X involved in the expression for Kc is represented by [X]

The value of the equilibrium constant is not affected either by changes in concentration or addition of a catalyst