Equilibrium

Question 1

1st year equilibrium: mention _____in answer

Answer 1

Effect on yield

Question 2

1st year equilibrium: 3 important points

Answer 2

• dynamic equilibrium
• homogeneous equilibrium
• equilibrium law

Question 3

dynamic equilibrium?

Answer 3

( equilibrium bit) Rate of forwards and backwards reactions are equal (dynamic bit) and reactions continue at a molecular level

Question 4

homogeneous equilibrium?

Answer 4

all particles in the equilibrium system are in the same state

Question 5

equilibrium law?

Answer 5

at eq., the [products]/ [reactants] = constant

• amounts of r and p don’t change

Question 6

Kc general?

Answer 6

• The eq. constant
• Kc tells us the relative proportion of reactants and products present at eq.
• [r] and [p] DO NOT CHANGE AT EQ.
• the units for Kc must be worked out for each question

Question 7

if there are no units?

Answer 7

must write no units,, can’t just leave it blank

Question 8

for the equilibrium constant?

Answer 8

need the conc at EQUILIBRIUM

Question 9

Equilibrium constant is constant unless

Answer 9

the temperature is changed.

Question 10

Kp vc Kc?

Answer 10

Kp for gases

Kc for liquids but Kc can be used for gases too

Question 11

Mole fraction, x, equation

Answer 11

Mole fraction = moles of the gas/ total n of all gases

Question 12

all x values add to?

Answer 12

1

Question 13

partial pressure is?

Answer 13

the contribution a gas makes to the total pressure

Question 14

partial pressure symbol

Answer 14

p

Question 15

total pressure symbol

Answer 15

P

Question 16

Partial pressure equation?

Answer 16

p = xP
pp = mole fraction x total pressure

Question 17

the sum of the partial pressure =?

Answer 17

total pressure

Question 18

Kp =

Answer 18

pproducts/ preactants

Question 19

when working out, K ignore?

Answer 19

solids, leave them out of the equation

Question 20

Effect of changing temp on K?

Answer 20

• ony thing that changes K
• an ⬆ in temp shifts the eq. in the endothermic direction
• a ⬇ in temp shifts the equilibrium in the exothermic direction
• value of K has to change w temp

Question 21

effect of increasing temp on K?

Answer 21

• of the forwards reaction is endothermic, and the temp is ⬆
• the equilibrium yield of the products would ⬆
• eq. yield of the reactants would decrease
• so K would decrease

the opposite is true for exothermic reactions when temp increases

Question 22

when explaining the impact of changing conc/ pressure on K include these in the answer

Answer 22

• Kc/Kp expression
• theoretically what would happen
• what actually happens - equilibrium shift
• impact on Kc - none

Question 23

impact of adding a catalyst on the value of K?

Answer 23

• does not change
• bc does not impact position of eq.
• the forwards and backwards reactions are sped up equally so eq is established faster

Question 24

Kp and Kc are?

Answer 24

temp dependent constants

Question 25

what happens when the pressure is increased but there are the same amount of moles on either side of the equation?

Answer 25

both sides impacted the same so no effect on K

Question 26

does the mole fraction change when the pressure is increased at a constant temp?

Answer 26

Yes. Increasing the P would cause the equilibrium to shift to the side with the fewest moles.
so the partial pressure would change and so the mole fraction must also change in the same way.

Question 27

Mpa to pa ?

Answer 27

x 10-6

Question 28

dm3 to m3?

Answer 28

dm3 / 1000

Question 29

(long q) the steps?

Answer 29

• initial n

* n at eq.

Question 30

(long q) the steps?

Answer 30

• initial n
• n at eq.
• ( total n at eq.) then x
• p = xP
• plug p into Kp equation

Question 31

why does the K value not change w changing [] or P?

Answer 31

• equilibrium shift (le Chatelier’s principle)
• the changes brought about by this balance
• so K doesn’t change

Question 32

theoretically, if P was increased which side increases tge most

Answer 32

the side with the most moles.

• if this side is the products, then K would theoretically increase
• if this side is the reactants, you are / by a bigger number so K would theoretically decrease

Question 33

Really, when P is changed what happens?

Answer 33

• if P is ⬆, then the side w the fewest n favoured and more of the thing on that side is made, less of the thing on the other side (smaller p)
• so K doesn’t change (essentially the changes balance)

Question 34

what happens when the conc of a substance is increased?

Answer 34

• eq. shifts to use up the extra substance
• so the conc of this substance ⬇
• and the conc of substances on the other side of the arrow ⬆
• so K does not change