Equilibria

Question 1

What does the term dynamic mean?

Answer 1

The forward and backward reactions are occurring simultaneously.

Question 2

Two features of dynamic equilibrium?

Answer 2

Forward and backwards reactions are occurring at equal rates.

The concentrations of reactants and products stay constant

Question 3

What is le Chatelier’s principle?

Answer 3

Le Chatelier’s principle states that if an external condition is changed the equilibrium will shift to oppose the change.

Question 4

How does temperature effect the position of equilibrium?

Answer 4

If the forward reaction is exothermic and the temperature is increased the equilibrium will shift to the left.

Question 5

How does pressure effect the equilibrium?

Answer 5

Increasing the pressure will shift the equilibrium to the side with fewer moles of gas.

Question 6

What are the 4 mark points you must say when answering an equilibrium question?

Answer 6

Equilibrium will shift to oppose condition

Why does it shift?

Direction the equilibrium will shift towards?

Talk about yield

Question 7

Why are high pressures not used often even if they produce product faster?

Answer 7

High electrical energy costs for pumping and the equipment is expensive

Question 8

If the concentration of the reactants is increased, how will the equilibrium change to combat this?

Answer 8

The equilibrium will shift to the right to make more product to decrease the concentration of the reactants.

Question 9

Effects of Catalysts on Equilibrium?

Answer 9

A catalyst has no effect on the position of equilibrium, it will speed up the rate at which equilibrium is achieved.

Question 10

What factors affect the Kc?

Answer 10

Temperature

Question 11

How does temperature effect KC?

Answer 11

Kc increases if the equilibrium shifts to the right and decreases if it shifts to the left.

Question 12

Why would an industrialist not choose a high temp and pressure for a reaction?

Answer 12

The reaction could be slower
Some pressures are expensive to obtain

Question 13

Explain why increasing temperature increases rate of reaction?

Answer 13

Particles have more energy
More collisions and so more successful collisions

Question 14

How to know whether a reaction has reached equilibrium?

Answer 14

The concentration of the reactants and products are constant

Question 15

If you have the equilibrium constant for the forwards reaction how do you calculate the equilibrium constant for the backwards reaction?

Answer 15

1/equilibrium constant

Question 16

What are the conditions needed for
CH₂CH₂(g) + H₂O ⇌ CH₃CH₂OH(l)?

Answer 16

300°C
70 atm
Concentrated H₃PO₄
High pressure gives good yield and high rate however too high a pressure would lead to higher energy costs for pumps to produce the pressure.

High pressure can also lead to polymerisation of ethene.

Question 17

What are the conditions needed for
CO(g) + 2H₂(g) ⇌ CH₃ OH(g)

Answer 17

400°C
50atm
Chromium and zinc oxides

Low temperature gets a good yield but a slow rate

High-pressure gives good yield and a high rate, too high a pressure would lead to higher energy costs for pumps to produce the pressure