19.1 - 19.3

Question 1

What are reversible reactions

Answer 1

• reactions that can go forwards and backwards

Question 2

What does concetration time graph look like for forwards and backward reactions

Answer 2

Question 3

Define the term dynamic equilibrium

Answer 3

• the point whew the rate of forwards reaction is equal to the rate of backwards reaction

Question 4

What is the only system dynamic equilibrium occur in

Answer 4

• closed systems

Question 5

What does a Kc expression look like for this reaction:
2A +B <=> 2C + D

Answer 5

• Kc= [C]^2 [D] Products
  ————- —————
  [A]^2 [B] Reactants

Question 6

What are the only states included in the Kc expression

Answer 6

• gases

Question 7

What can you work out before working out Kc

Answer 7

• the concentration of a species

Question 8

What is the acronym you need to remember to work out the concentration of a species in equilibrium

Answer 8

• I.C.E
  (Initial moles, change in moles, equilibrium moles)

Question 9

Answer this question:

Answer 9

• Kc= 0.050moldm^-3
  1) do ICE
  2) divide equilibrium mole by volume to find concentration
  3) put concentrations into Kc to get answer

Question 10

Answer this question:

Answer 10

Answer= 4.49moldm^-3

Question 11

What is the total pressure in a reaction

Answer 11

• the same of all the pressures in individual gases (partial pressure)

Question 12

Answer this question:

Answer 12

Question 13

How are partial pressures calculated

Answer 13

• using mole fractions

Question 14

What are mole fractions

Answer 14

• the proportion( fraction) of a gas in a gas mixture

Question 15

What is the equation for the mole fraction of a gas

Answer 15

Number of moles of gas
————————————————
Total number of gas in the mixture

Question 16

Answer this question:

Answer 16

p (SO2Cl2)= 188kPa

Question 17

What are partial pressures used to calculate

Answer 17

• Kp

Question 18

What is Kp

Answer 18

• the gas equilibrium

Question 19

What does a Kp reaction look like for this reaction:
2A(g) + B(g) <=> C(g) + D(g)

Answer 19

• Kp= p(C) p(D)
  -—————-
  p(A)^2 p(B)

Question 20

What are the units for pressure

Answer 20

• KPa
• atm

Question 21

What is the only state that Kp include

Answer 21

• gases

Question 22

What does Le Chatelier’s principle state

Answer 22

• If a reaction is subjected to a change in external variable then the positions of the equilibrium moves to counteract this change

Question 23

What happens when the equilibrium shifts to the left

Answer 23

• make more reactants

Question 24

What happens when the equilibrium shifts to the right

Answer 24

• we make more product

Question 25

What happens if you increase the concentration of a reactant or product produced according to Le Chatlier’s principle

Answer 25

- The equilibrium will shift to try and reduced the concentration

Question 26

What happens if you increase the pressure of a reactant or product produced according to Le Chatlier’s principle

Answer 26

- the equilibrium will shift to the side with less number of moles to counteract this change

Question 27

What happens if you increase the temperature of a reactant or product produced in an exothermic reaction according to Le Chatlier’s principle

Answer 27

- the equilibrium will move to the endothermic to try and reduce the temperature

Question 28

What affects do catalyst have on the position of equilibrium

Answer 28

- NO EFFECT - only speed up the rate of the forward and backward reaction equally

Question 29

What is the affect of temperature on Kp

Answer 29

- Kp is only valid for one temperature - changing temp will change equilibrium so also Kp

Question 30

If temperature causes equilibrium to shift to the right what happens to the value of Kp

Answer 30

- it increases

Question 31

If temperature causes equilibrium to shift to the left what happens to the value of Kp

Answer 31

- Kp decrease

Question 32

What is the affects of pressure on the value of Kp

Answer 32

- Kp is UNAFFECTED by any changes in Kp

Question 33

What is the affects of catalyst on the value of Kp

Answer 33

- NO EFFECT ON Kp - only speeds up the forwards and backward reaction

Question 34

What affects the value of Kc

Answer 34

- temperature

Question 35

What is the affects of temperature on the value of Kc

Answer 35

- only valid for one temperature - changing temperature will change the equilibrium concentrations so Kc will change too

Question 36

What happens to the value of Kp if temperature change causes equilibrium to shift right

Answer 36

- value of Kp increases

Question 37

What happens to the value of Kp if temperature change causes equilibrium to shift left

Answer 37

- value of Kp decreases

Question 38

What affect does concentration have on the value of Kc

Answer 38

- NO AFFECT

Question 39

What affect does concentration have on the value of Kc

Answer 39

- NO EFFECT - only speeds up the rate of the forward and backward reaction