Equilibrium

Question 1

What are the features of a dynamic equilibrium?

Answer 1

the rate of the forward reaction is the same as the rate of the reverse reaction
the system must be closed
the conc of each substance involved remain constant

Question 2

What is a closed system?

Answer 2

it is not possible for reactants or products to enter or leave the system

Question 3

What is the enthalpy change equation?

Answer 3

change in enthalpy = Ea (forwards) - Ea (backwards)
forwards - reactants
backwards - products

Question 4

What is Le chatelier’s principle?

Answer 4

when one of the conditions affecting the position of a dynamic equilibrium is altered, the position of equilibrium will shift in the direction that opposes the change

Question 5

What happens to the equilibrium when you increase the temp of a reaction?

Answer 5

shifts to the endothermic direction because the system tries to decrease the temp

Question 6

What happens to the equilibrium when you decrease the temp of a reaction?

Answer 6

equilibrium shifts to the exothermic direction as the system tries to raise the temp

Question 7

What does shift mean in terms of equilibrium?

Answer 7

settling into a new equilibrium

Question 8

What happens to the equilibrium when you increase the conc of the reactants?

Answer 8

the system tries to reduce them so equilibrium shifts to the right to produce more product

Question 9

What happens to the equilibrium when you decrease the conc of a product?

Answer 9

system tries to increase the products so shifts to the right to oppose the change

Question 10

How do you increase pressure?

Answer 10

decrease the volume by compressing gas in a syringe

Question 11

What happens to the equilibrium when you increase the pressure of a reaction?

Answer 11

system wants to decrease the no. of mol sp equilibrium shifts to the side where there are fewer moles of gas

Question 12

What happens to the equilibrium when you decrease the pressure of a reaction?

Answer 12

the system tries to increase the pressure by decreasing the no. of mol - shifts to the side with larger moles of gas

Question 13

What colour is dichromate ions?

Answer 13

orange

Question 14

What colour are chromate ions?

Answer 14

yellow

Question 15

What does a catalyst do to equilibrium?

Answer 15

causes NO shift but speeds up the forward reaction so reached equilibrium sooner

Question 16

What do you need to discuss on conditions for industrial processes for full marks?

Answer 16

1. effect on equilibrium yeild - le chat
2. effect on ROR - collision theory
3. cost and safety

Question 17

What is an industrial process that is an example of balancing equilibrium?

Answer 17

the haber process

Question 18

What is the symbol for the equilibrium constant?

Answer 18

Kc

Question 19

How can you tell if the equilibrium shifts to the right from kc value?

Answer 19

the bigger the Kc value - the further to the right the equlibrium position
if the Kc value is bigger than 1

Question 20

What is the collision theory?

Answer 20

for a reaction to occur, molecules need to collide

Question 21

What does the collision theory state that molecules need to react?

Answer 21

the correct molecular orientation
molecules must physically collide
molecules must have enough energy to break and form bonds

Question 22

What does it mean by the correct molecular orientation?

Answer 22

attacking the oppositely charged side of a molecule = electrostatic attraction causes molecules to collide

Question 23

What does the area under the boltzmann distribution curve represent?

Answer 23

the total no. of molecules in the system

Question 24

Why doesn’t the boltzmann distribution curve never touch the x axis?

Answer 24

there is no maximum energy that molecules can have

Question 25

Explain the effect of using a catalyst has on a reaction using the boltzmann distribution curve

Answer 25

the Ea is lowered therefore larger proportion of molecules are above the Ea

Question 26

What is the effect of increasing temp on the boltzmann distribution curve ( the curves shape)?

Answer 26

the area under the curve is the same
the curve shifts to the right
the height of the peak falls

Question 27

What are the 2 effects of increasing temp on a reaction using the boltzmann distribution curve?

Answer 27

1. molcules have more KE so there is an increased frequency of collisions
2. the no. of molecules with energy higher than the Ea has increased substantially, so there is a greater proportion of collisions that are successful