chemical equilibrium

Question 1

Closed system

Answer 1

• a system in which mass is conserved inside the system but energy can enter or leave the system freely

Question 2

Open system

Answer 2

• a system in which both energy and matter can be exchanged between the system and its surroundings

Question 3

forward vs. reverse reaction

Answer 3

• products can be produced into products

- products can be produced back into products

Question 4

dynamic chemical equilibrium

Answer 4

• forward and reverse reactions are taking place at the same rate
• constant concentration
• closed system and reversible reaction must exist
• rate of forward reaction = rate of reverse reaction

Question 5

Le Châteliers principle

Answer 5

• When an external stress (change in pressure, temperature or concentration) is applied to a system in dynamic chemical equilibrium, the equilibrium point will change in such a way as to counteract the stress

Question 6

phase equilibrium

Answer 6

• a state of dynamic equilibrium between liquid and vapour faze

Question 7

equilibrium state

Answer 7

• dynamic, not stopped and both reactions occur at the same rate
• closed system
• concentrations remain constant
• looks as if reaction has stopped, but is continuous
• reached from either direction

Question 8

Le Châteliers principle steps

Answer 8

• identify disturbance
• state system will oppose disturbance
• forward or reverse is favoured
• result, observation

Question 9

concentration changes

Answer 9

• solvent and solution (solid won’t change, pure liquid density won’t change)

Question 10

pressure

Answer 10

• only applies to gasses (any gas in either of the reactions)
• larger volume (increase) = less pressure (decrease), more moles of gas
• lesser volume (decrease) = more pressure (increase), less moles of gas
• increase in pressure due to decrease in volume
• side with less moles is favoured
• forward or reverse is favoured
• yield of favoured is increased
• new equilibrium is formed

Question 11

temperature

Answer 11

• increase
• shift to side that opposes
• endothermic is favoured
• decrease
• shift to side that opposes
• exothermic is favoured

Question 12

catalyst

Answer 12

• increases rate of reaction

Question 13

LCP

Answer 13

• stress
• counter
• favoured reaction
• result

Question 14

Kc effects

Answer 14

• temperature
• no effects
• pressure
• concentration

Question 15

concentration increase (rate time graph)

Answer 15

• substance increase
• opposes this decreasing amount of substance
• see and increase in other substance
• gradually increases until equal again

Question 16

change in pressure (rate time graph)

Answer 16

• sharp increase / decrease in all substances

Question 17

change in temperature (rate time graph)

Answer 17

• affects either endothermic or exothermic

Question 18

catalyst (rate time graph)

Answer 18

• increase both rates

Question 19

change in concentration (concentration time graph)

Answer 19

• sharp change

- gradual change in other substance till equilibrium

Question 20

change of temperature (concentration time graph)

Answer 20

• sharp change

- one of either the products or the reactants changed in one direction the other in the other direction

Question 21

catalyst (concentration time graph)

Answer 21

• no change if at equilibrium already