Mod 5 Factors affecting equilibrium

Question 1

What does Le Chatelier’s Principle state?

Answer 1

If a system at equilibrium is subject to change in conditions, the system will behave in a way to partially counteract the change and re establish equilibrium

Note: don’t state the definition of LCP during exam

Question 2

What steps should be used when using LCP to predict changes to a reversible system?

Answer 2

1. What change is imposed?
2. What is the opposite of the change? (this is what the system will do to counteract the change)
3. Which reaction direction is favoured? (forward or reverse)
4. Does equilibrium shift to the left or right?
5. What happens to the concentration of each aqueous substance or gaas?
6. Mention how equilibrium will be re-established

Question 3

How will an increase in concentration of reactants affect equilibrium? (explain through LCP)

Answer 3

Cause the rate of the forward reaction to increase, while reverse reaction won’t be affected. Equilibrium shifting in favour of products

According to LCP: addition of reactant –> system responds by removing reactants, thus favouring the forward reactiion, and shifting equilibrium to right

Question 4

How will a decrease in concentration of products affect equilibrium? Explain through LCP

Answer 4

Rate of backward reaction will decrease, and there will be a shift in equilibrium in favour of the products. According to LCP, removal of a product causes system to respond by making more product, thus favouring the forward reaction, so equilibrium shifts right

Question 5

What are the effects of an increase and a decrease in concentration of a reactant?

Answer 5

Increase in concentration of reactant: Equilibrium shifts right

Decrease in concentration of reactant: Equilibrium shifts to the left

Question 6

What are the effects of an increase and a decrease in concentration of a product?

Answer 6

Increase in concentration of a product: Equilibrium shifts to the left

Decrease in concentration of a product: Equilibrium shifts right

Question 7

What are the 4 ways that an equilibrium system can be disturbed by?

Answer 7

By making changes in:

Concentration
Temperature
Volume
Pressure

Question 8

How does an increase in volume impact equilibrium? Explain using LCP

Answer 8

An increase in volume of a gaseous system will decrease the pressure of the overall system. LCP states that the system will attempt to partially counteract the change through increasing the pressure of the overall system through favouring the reaction which produces the most gaseous moles.

An increase in volume of a solution (i.e. adding water) will decrease the concentration of the oveerall system. LCP states that the system will attempt to partially counteract the change through increasing the concentration of the overall system through favouring the reaction which produces the most aqueous moles.

Question 9

How does a decrease in volume impact equilibrium? Explain using LCP.

Answer 9

A decrease in volume of a gaseous system will increase the pressure of the overall system. LCP states that the system will attempt to partially counteract the change through decreasing the pressure of the overall system through favouring the reaction which produces the least gaseous moles.

An decrease in volume of a solution (i.e. removing water or part of solution) will increase the concentration of the overall system. LCP states that the system will attempt to partially counteract the change through decreasing the concentration of the overall system through favouring the reaction which produces the least aqueous moles.

Question 10

Why is it that an exothermic or endothermic reaction impacts how temperature affects equilibrium?

Answer 10

An increase in temp will favour the endothermic reaction. This is because system will attempt to reduce the temperature through absorbing excess heat for the reaction (thus endothermic)

A decrease in temp will favour the exothermic reaction. This is because the system will attempt to increase the temperature through releasing excess heat for the reaction (thus exothermic)

Question 11

Rate time graphs

Answer 11

Check book for notes on rate time graphs

Question 12

What is an important equation to remember for demonstrating Concentration and temperature?

Answer 12

(Co(H2O)6) 2+ + 4Cl- + Heat ⇌ (CoCl4)2- + 6H2O (l), delta H > 0

Dehydration of cobalt chloride hexahydrate is not reversible, however when dehydrated cobalt (II) chloride is dissolved in water, it forms an equilibrium between the hydrteed and dehydrated forms of cobalt (II) chloride. It is an exothermic reaction

Adding and removing chlorides (removal of chlorides by adding silver nitrate as precipation will form)

Temperature - equilibrium is endothermic, if heat increases, equilibrium will shift to the right

Question 13

What colour is dehydrated cobalt chloride?

Answer 13

blue

Question 14

What colour is hydrated cobalt chloride?

Answer 14

Pink

Question 15

What coloour is NO2 gas?

Answer 15

Broown gas

Question 16

What coloour is N2O4?

Answer 16

Clear gas

Question 17

What is the N2O4 and NO2 equilibrium reaction? Exo or endothermic?

Answer 17

N2O4 (g) + HEAT ⇌ 2NO2 (g). Endothermic

Question 18

What examples should be discussed with the dinitrogen tetroxide and nitrogen dioxide reaction? (i.e., changes to concentration, changes to pressure) (2)

Answer 18

Changes to temp, changes to pressure

Question 19

What are the 3 equations that are essential to remember for equilibrium reactions? With respective colours

Answer 19

N2O4 (g) + HEAT ⇌ 2NO2 (g) (clear to brown)

(Co(H2O)6) 2+ + 4Cl- + Heat ⇌ (CoCl4)2- + 6H2O (l) (Pink to blue)

Fe3+ (aq) + SCN- (aq) ⇌ FeSCN 2+ (aq) (yellow to deep red)

Question 20

What colour ar iron (III) ions?

Answer 20

Yellow

Question 21

What colour is Iron (III) thiocyanate

Answer 21

Deep red