Topic 10 Equilibrium

Question 1

What is the definition of dynamic equilibrium? Why?

Answer 1

The conc of reactants and products reach a point where they stay constant
Because rate of forward reaction is EQUAL to backward reaction

Question 2

What is Le Chatelier’s principle?

Answer 2

“A system in dynamic equilibrium will react to oppose any changes made to it”

Question 3

If more ammonia is added to the Haber process, equilibrium will shift….

Answer 3

To the left hand side,
Ammonia concentration is reduced

Question 4

If my hydrogen is added to the haber process, equilibrium will shift to….

Answer 4

The right hand side, removing the extra hydrogen

Question 5

What is the Effect of pressure in equilibrium system? If pressure is increased, equilibrium shifts…

Answer 5

To the side with less number of molecules

Question 6

If temperature is increased, the equilibrium will shift…

Answer 6

To the endothermic direction

Question 7

If the temperature is decreased in an equilibrium system, the equilibrium will shift….

Answer 7

To the exothermic direction

Question 8

In what conditions do change of pressure affect equilibrium?

Answer 8

When reactants and products are gaseous

Question 9

What are 4 features of a system in dynamic equilibrium? (2 marks)

Answer 9

• forward rate of reaction is equal to backward reaction
• conc of both are constant

(- all reactants and products are present)
(- both reactions occurring simultaneously ))

Question 10

What are industrial conditions for Haber-Bosch process?

Answer 10

400-450 C
200 atm
Powdered iron catalyst

Question 11

How to achieve a better yield in Haber process?

Answer 11

• lower temp (but slows RoR)
• higher pressure (but very expensive)

Question 12

What is the contact process?

Answer 12

Making sulphuric acid (H2SO4)
From S and O2 making SO2, then 2SO2(g)+O2(g)⇌2SO3(g)
Then SO3(g) + H2O(l) ⇌ H2SO4(aq) [sulphur trioxide + water -> sulphuric acid]

Question 13

What are conditions needed for contact process?

Answer 13

450 C
2 atm
Catalyst V2O5 (Vandium (V) oxide)

Question 14

What is the Haber process?

Answer 14

Processing making ammonia NH3

Question 15

What is a homogeneous system?

Answer 15

All reactants and products are the in the same state

Question 16

What are heterogeneous systems?

Answer 16

System with components that has at least two different phases are present.

Question 17

What state do we leave out when calculating Kc?

Answer 17

Solids!

Question 18

How to calculate Kc?

Answer 18

[PRODUCTS]/[REACTANTS]
If the equation was: A+ B –> C + 2D, the Kc equation would become: [C] [D]2 / [A] [B]

[X]^n n=moles

Question 19

What does [A] mean in Kc equation?

Answer 19

Concentration of A (moldm-3)

Question 21

What happens when you compress a gas with colour in equilibrium immediately ?

Answer 21

Mixture always goes darker IMMEDIATELY first and then shift to the correct side
Even though equilibrium doesn’t favour that reaction!

Question 22

Why does nano particles increase rate of reaction over powder? 2 marks

Answer 22

• higher surface area of contact
• more frequent collisions

Question 23

Why does change of pressure change rate of reaction? 3 marks

Answer 23

• increase pressure increases RoR
• as particles are closer together
• more frequent collisions

Question 24

Why does student choose polystyrene cup instead of glass beaker?

Answer 24

More insulating to reduce heat loss

Question 25

What the unit for Kc? (Equilibrium constants)

Answer 25

mol dm -3 each
Cancel out when
[products]^a / [reactants]^b

Question 26

Why do test tubes need to be put in water bath before equilibrium reaction?

Answer 26

Allow solutions to reach same temp and equilibriate

Question 27

What state is is left out when calculating equilibrium constants (Kc)? Why?

Answer 27

Solids only, as the conc stays constant
Gases do seperately