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A Level Chemistry 1 > Equilibrium > Flashcards

Equilibrium Flashcards

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1
Q

What is Kc

A

equilibrium constant, has a fixed value at a specific temperature

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2
Q

What is the equilibrium constant expression?

A

write it down on paper

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3
Q

high value of Kc

A

equilibrium lies to right, favors production of products, reaction almost completed

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4
Q

low value of Kc

A

equilibrium lies to left, favors reactants, reaction barely started

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5
Q

What is the purpose of the constant Kc?

A

to inform us of the nature of equilibrium (where it lies). But, it doesn’t tell us how quickly the equilibrium state is reached

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6
Q

If Q=Kc, Q>Kc, Q

A
  • Q=Kc: equilibrium is reached
  • Q>Kc: proceed to favor reactants, shift to left
  • Q
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7
Q

What is the value of Kc in an inverse reaction?

A

Kc’, 1/Kc, Kc-1

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8
Q

What is the value of Kc in a multiple of a reaction?

A

Kc^x

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9
Q

What is the value of Kc when the reaction coefficients are halved?

A

square root Kc

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10
Q

What is the value of Kc when two reactions are added together?

A

Kc^i x Kc^ii

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11
Q

What do industries use equilibrium for?

A

to determine conditions that will maximize the yield of a product

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12
Q

evaporation

A

liquid to vapour state

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13
Q

condensation

A

vapour to liquid

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14
Q

dynamic equilibrium

A

forward and backward reactions are still occurring even though it doesn’t look like it

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15
Q

Forward reaction

A

left to right, reactants to products

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16
Q

Backward reaction

A

right to left, products to reactants

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17
Q

Specific characteristics of equilibrium (5)

A
  • dynamic
  • achieved in closed system so no exchange of matter with surroundings
  • concentrations of reactants and products remain constant because they’re being produced and destroyed at an equal rate
  • no change in macroscopic properties because concentration is constant (color or density)
  • can be reached from either direction
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18
Q

Le Chatelier’s principle

A

system at equilibrium when subjected to a change will respond in such a way to minimize the effect of the change

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19
Q

What happens when the concentration of a reactant increases?

A
  • forward reaction increases, rate of reactions no longer equal
  • at equilibrium, equilibrium favors production of products, shifts to right
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20
Q

What happens when a product is removed or it decreases in concentration?

A
  • backward reaction decreases, rate of reactions no longer equal
  • equilibrium favors production of product, shift to right
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21
Q

What happens when pressure is increased?

A

equilibrium shifted to side with smaller number of particles

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22
Q

What happens when pressure is decreased?

A

equilibrium shifted to side with greater number of particles

23
Q

Exothermic reactions

A
  • temperature always decreases
  • enthalpy negative
  • favors production of products, equilibrium shifts to right
  • product particles don’t have enough energy to form bonds
  • takes less energy to form bonds with products
  • increased value of Kc
24
Q

Endothermic reactions

A
  • temperature always increases
  • enthalpy positive
  • favors production of reactants
  • equilibrium shifted to left
  • decreased value of Kc
  • takes less energy to break bonds than it does to make them
25
Q

Where does equilibrium shift for exothermic reactions?

A

to the right, higher yield of products at a lower temperature

26
Q

Where does equilibrium shift for endothermic reactions?

A

to the left

27
Q

Effect of concentration, pressure, temperature, catalyst on Kc

A

nothing changes the value except temperature

28
Q

What is one dilemma we come across with exothermic reactions?

A

at a lower temperature, there is a lower rate of reaction, and it takes longer to produce a high yield of products

29
Q

What does a catalyst do? How do they affect the equilibrium state?

A
  • speeds of rate of reaction by providing alternate reaction pathway with a lower activation energy
  • not chemically changed after reaction
  • speed up attainment of equilibrium state by making products form faster
30
Q

Draw and label an energy diagram

A

Label:

  • Ea of forward and backward reaction
  • reactants and products
31
Q

At high temperatures, the _______ reaction is favored. At low temperatures, the ______ reaction is favored.

A
  • high temp= endothermic

- low temp= exothermic

32
Q

At high temperatures, the _______ reaction is favored. At low temperatures, the ______ reaction is favored.

A
  • high temp= endothermic

- low temp= exothermic

33
Q

What is the goal for industrial companies in their processes?

A
  • high rate of reaction

- equilibrium lies to the right to produce high yield of products

34
Q

Draw the reaction the haber process is based upon.

A

N2+ 3H2 +_ 2NH3

35
Q

Is the forward reaction of the haber process exothermic or endothermic?

A

exothermic

36
Q

Three key things to know for the Haber process:

A
  • reactants and products are gases
  • change in number of gas molecules as reaction proceeds
  • forward reaction is exothermic, backwards is endothermic
37
Q

How is concentration used to benefit industries? Haber process.

A
  • nitrogen and hydrogen have 1:3 ratio

- ammonia is removed once it forms, causing equilibrium to shift to right to favor products

38
Q

How is pressure used to benefit industries? Haber process.

A
  • because there are less molecules on the right than the left( 2 on right, 4 on left), favored by high pressure
  • more ammonia made
  • optimum pressure: 2 x 10^7
39
Q

Optimum pressure for haber process

A

2 x 10^7

40
Q

How is temperature used to benefit industries? Haber process.

A
  • forward reaction exothermic, so favored by lower temperature
  • moderate temperature of 450 degrees
41
Q

Temperature of Haber process

A

450 degrees

42
Q

Catalyst of Haber process

A

iron with small amounts of aluminum and magnesium oxides

43
Q

Catalyst of Haber process

A

iron with small amounts of aluminum and magnesium oxides

44
Q

Write out the three steps of the Contact Process with equations.

A
  1. Combustion of sulfur to form sulfur dioxide
  2. Sulfur dioxide oxidizes to form sulfur trioxide.
  3. Sulfur trioxide reacts with water to form sulfuric acid.
45
Q

Is the forward process of the Contact Process exothermic or exothermic?

A

exothermic

46
Q

Describe pressure of Contact Process to create sulfuric acid.

A
  • 3 molecules on right and 2 on left, reaction favored by high pressure
  • equilibrium shifts to right
  • produces more sulfur trioxide
  • 2 x 10^5 Pa
47
Q

Describe temperature of Contact Process to create sulfuric acid.

A
  • forward reaction exothermic

- moderate temperature of 450 degrees celsius

48
Q

Describe catalyst of Contact Process to create sulfuric acid.

A

Vanadium (V) Oxide

49
Q

Too low a temperature for processes does what?

A

increase the yield, but decrease the rate at which it produces yield

50
Q

What is the pressure of the Contact process?

A

2 x 10^5

51
Q

Pressure of methanol production

A
  • 5-10 x 10^6 Pa
  • 3 to 1 molecules means high pressure will favor product
  • equilibrium shifts to right
52
Q

Temperature of methanol production

A
  • forward reaction is exothermic

- 250 degrees celsius

53
Q

Catalyst of methanol production

A
  • Cu - Zno - Al2O3

A Level Chemistry 1 (11 decks)

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