Equilibria

Question 1

What type of reaction reaches an dynamic equilibrium state?

Answer 1

All reversible reactions

Question 2

Name two features of dynamic equilibrium?

Answer 2

Forward and backwards reactions occur at the same rate

Concentration of reactants and products stay constant

Question 3

What do we use position of equilibrium for?

Answer 3

To describe the composition of the equilibrium mixture

Question 4

What happens if the position of equilibrium favoured reactants?

Answer 4

The equilibrium mixture would be mostly reactants

Question 5

What does Le Chatelier’s principle state?

Answer 5

If an external condition is changed the equilibrium will shift to try to oppose the change (and try to reverse it).

Question 6

What is Le Chatelier’s principle used for?

Answer 6

To work out how changing external conditions such as temperature and pressure affect the position of equilibrium.

Question 7

What will the equilibrium do if the temperature is increased?

Answer 7

The equilibrium will shift to try to oppose this and move to oppose this and move in the endothermic direction to try and reduce the temperature by absorbing heat

Question 8

What will the equilibrium do if the temperature is decreased?

Answer 8

The equilibrium will try to oppose this and move in an endothermic direction to try and increase the temperature given out heat.

Question 9

What might low temperatures do to the yield?

Answer 9

Low temperatures may give a higher yield of product but may also result in slow rates of reaction. Often a compromise temperature is used that gives a reasonable yield and rate.

Question 10

What will increasing the pressure do to the equilibrium position?

Answer 10

It will shift the equilibrium towards the side that has fewer moles of gas to oppose the change and thereby reduce the pressure

Question 11

What will decreasing the pressure do to the equilibrium position?

Answer 11

Shift the equilibrium towards the side with more moles of gas to oppose the pressure and thereby increase the pressure

Question 12

What happens if the number of gas is equal on both sides of the equation if the pressure is changed?

Answer 12

Nothing

Question 13

What does the term dynamic mean?

Answer 13

Both forwards and backwards reactions are occurring simultaneously

Question 14

What would increasing the pressure do to the yield of product?

Answer 14

It would increase it and give a faster rate

Question 15

What would increasing the pressure do to cost?

Answer 15

Increase them

Industrially high pressures are expensive to produce and the equipment to contain the high pressure is expensive

Question 16

Why are Industrially high pressures are expensive to produce?

Answer 16

High electrical costs for pumping gases to make high pressure

Question 17

What goes increasing OH- ions do to the equilibrium?

Answer 17

Shifts them to oppose this and move in a forward direction to remove and decrease the concentration of OH ions
It will shift to the reverse reaction giving higher yield

Question 18

What does adding H+ do to solution?

Answer 18

Reduces the concentration so the equilibrium shift back to the forward reaction giving brown colour.

Question 19

Explain effect of catalyst on equilibrium?

Answer 19

No effect on rate of equilibrium but will speed up rate of which equilibrium is achieved

Question 20

Why doesn’t a catalyst affect the equilibrium?

Answer 20

It speeds the forwards and backwards reactions by the same amount

Question 21

Habour process equation?

Answer 21

N2(g) + 3H2(g) 2NH3(g) + 92.4 kJ

Question 22

Conditions used for habour process?

Answer 22

450oC
200-1000 atmospheric pressures
Iron catalyst

Question 23

Why isn’t a lower temperature used for habour process?

Answer 23

Gives good yield but slow rate

Compromise condition

Question 24

Why isn’t a higher pressure used?

Answer 24

Gives good yield and high rate but expensive to maintain pressure (building+ electricity pumping)

Question 25

Enthalpy change for habour process?

Answer 25

• negative

Exothermic