Chemical Equib

Question 1

Define a Closed System:

Answer 1

A closed system is a system in which mass is conserved inside the system, but energy can enter or leave the system freely.

Question 2

Define a Open System:

Answer 2

An open system is a system in which both energy and matter can be exchanged between the system and its surroundings.

Question 3

State Le Chatelier’s principle:

Answer 3

When an external stress is applied to a system in chemical equilibrium, the equlibrium point will change in such a way as to counteract the stress

Question 5

What is chemical equilibrium?

Answer 5

Chemical equilibrium is a dynamic equilibrium when the rate of the forward reaction equals the rate of the reverse reaction.

Question 6

What factors can affect equilibrium?

Answer 6

• concentration
• temperature
• pressure

Question 7

What are the steps in describing an equilibrium shift - according to Le Chatelier?

Answer 7

1) Identify the disturbance (external stress)

2) State le chateliers principal

3) system response (how does the system counteract external stress)

4) state favoured reaction (forward/reverse)

5) Discuss results (equilibrium shift, change in colour/concentration/pressure/temperature)

Question 8

How will equilibrium shift to decrease any increase in concentration?

Answer 8

• Added reactant -> forward reaction favoured.
• Added product -> reverse reaction favoured.

Question 9

How will equilibrium shift to increase any decrease in concentration?

Answer 9

• Removing reactant -> reverse reaction favoured.
• Removing products -> forward reaction favoured.

Question 10

Changing the mass of pure solids or volume of liquids will not disrupt…

Answer 10

Changing the mass of pure solids or volume of liquids will not disrupt the equilibrium or change rate of reactions.

Question 11

Equilibrium will shift to the ___ ___ if the temperature is increased.

Answer 11

Equilibrium will shift to the endothermic reaction if the temperature is increased.

Question 12

Equilibrium will shift to the ___ ___ if the temperature is decreased.

Answer 12

Equilibrium will shift to the exothermic reaction if the temperature is increased.

Question 13

What is the only change that affects Kc?

Answer 13

Temperature is the only change that affects Kc.

Question 14

An increase in temperature increases the the rate of ___ ___ ___ ___ ___ ___ but shifts the ___ ___

Answer 14

An increase in temperature increases the the rate of both the forward and the reverse reaction, but shifts the equilibrium position.

Question 15

Why is endothermic reaction most affected by temperature increase?

Answer 15

• Endothermic reactions have higher activation energy than exothermic reactions.

Question 16

What will happen if there is an increase in pressure in a closed system?

Answer 16

• Equilibrium will shift to decrease any increase in pressure by favouring the reaction direction that produces less molecules.

Question 17

What will happen if there is an decrease in pressure in a closed system?

Answer 17

• Equilibrium will shift to increase any decrease in pressure by favouring the reaction direction that produces more molecules.

Question 18

If Kc > 1

Answer 18

If Kc > 1 then equilibrium lies to the right. (More products than reactants)

Question 19

If Kc < 1

Answer 19

If Kc < 1 then equilibrium lies to the left.
(more reactants than products)

Question 20

As temperature increases, the Kc value ___

Answer 20

As temperature increases, the Kc value falls.

Question 22

When can chemical equilibrium be achieved?

Answer 22

Chemical equilibrium can only be achieved in a closed system.