topic 4: chemical equilibrium

Question 1

explain what happens in an open chemical system

Answer 1

energy and matter move freely between the system and surroundings

Question 2

explain what happens in a closed chemical system

Answer 2

energy can move between the system and surroundings but matter cant

Question 3

explain what happens in an isolated chemical system

Answer 3

neither energy nor matter can move between the system and the surroundings

Question 4

which of the 3 chemical systems is used in equilibrium reactions

Answer 4

closed

Question 5

explain what is meant by dynamic equilibrium

Answer 5

a point where the forward and reverse reactions occur at the same rate

Question 6

what can be stated about the reactants and products at dynamic equilibrium

Answer 6

at this point the concentrations of reactants and products remain constant butt they are rarely equal

Question 7

explain what is meant by the equilibrium lying to the right

Answer 7

the forward reaction is favoured, and more product is made

Question 8

explain what is meant by the equilibrium lying to the left

Answer 8

the reverse reaction is favoured and more reactant remains

Question 9

what does le chatelier’s principle state

Answer 9

“if a system at equilibrium is subjected to change the system reajustes itself to counteract the change”

Question 10

the three main factors afftecting an equilibriums position

Answer 10

•concentration
•temperature
•pressure

Question 11

consider: A+2B ⇌C+D

what happens if the concentration of A or B is increased

Answer 11

•equilibrium shifts to bring [A/B] back down
•more A+B react so forward reaction is favoured
•equilibrium shifts right (more product)

Question 12

consider: A+2B ⇌C+D

what happens if the concentration of A or B is decreased

Answer 12

•equilibrium shifts to bring [A/B] back up
•more C+D react to make more A+B
•reverse reaction is favoured (more reactant)
•equilibrium position shifts left

Question 13

consider: A+2B ⇌C+D

what happens if the concentration of C or D is increased

Answer 13

•equilibrium shifts to bring [C/D] back down
•more C+D is converted back into reactants
•reverse reaction is favoured (more reactant)
•equilibrium position shifts left

Question 14

consider: A+2B ⇌C+D

what happens if the concentration of C or D is decreased

Answer 14

•equilibrium shifts to bring [C/D] back up
•more A+B is converted into products
•forward reaction is favoured (more product)
•equilibrium position shifts right

Question 15

if the forward reaction us exothermic what will the reverse be

Answer 15

endothermic

Question 16

in an exothermic reaction what happens the the equilibrium when there is temperature increase

Answer 16

•system shifts to bring the temp back down
•reverse reaction will be favoured to absorb the additional heat
•equilibrium shifts left, favouring reactants

Question 17

in an exothermic reaction what happens the the equilibrium when there is temperature decrease

Answer 17

•system shifts to raise the temp
•favours the reaction that releases heat- the forward exothermic reaction
•equilibrium shifts right, favouring products

Question 18

describe the result of a pressure increase on this equilibrium

A+2B ⇌C+D
3 moles-2 moles

Answer 18

•equilibrium shifts to decrease the pressure (less molecules)
•shifts to the right, favouring the forward reaction

Question 19

describe the result of a pressure decrease on this equilibrium

A+2B ⇌C+D
3 moles-2 moles

Answer 19

•equilibrium shifts to increase the pressure (more molecules)
•shifts to the left, favouring the reverse reaction

Question 20

explain what happens in an equilibrium with a catalyst

Answer 20

a catalyst doesn’t effect the position of an equilibrium it just decreases the time taken for a reaction to reach equilibrium