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Chemistry > Topic 7: Equilibrium > Flashcards

Topic 7: Equilibrium Flashcards

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1
Q

Chemical Equilibrium

A
  • forward and backward reaction occur at the same rate
  • concentration of reactants and products remain constant
  • can only occur in a closed system
  • equilibrium is dynamic, meaning at a microscopic level the reaction does not stop and the reactants are continuously changing to products and the products are continuously changing into reactants
  • there is no change in the any physical properties
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2
Q

Physical Equilibrium

A
  • does not involve a chemical reaction, rather a change in state
  • the rate of the foward reaction = the rate of the backward reaction
  • the volume of liquid remains constant
  • can only occur in a closed system
  • equilibrium is dynamic, meaning at a microscopic level, the liquid is continuously getting evaportated and the gas is continuously getting condensed
  • physical preoperties remain the same
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3
Q

Equilibrium Constant

A
  • is the ratio between the concentration of products and the concentration of reactants
  • can only be changed by temperature
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4
Q

Equilibrium Constant Formula

A

aA + bB ⇄ cC + dD

Kc = ([C]^c [D]^d)/([A]^a [B]^b)

Kc = products ÷ reactants

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5
Q

What does a large Kc value show?

A
  • concentartion of products is greater than concentration of reactants at equilibrium
  • foward reaction is favoured
  • mixture mostly contains products
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6
Q

What does a small Kc value show?

A
  • concnetration of reactants is gretaer than concentration of products at equilibrium
  • backward reaction is favoured
  • mixture mostly contains reactants
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7
Q

What does Kc = 1 show?

A
  • there are equal amounts of reactants and products
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8
Q

Reaction Quotient

A
  • a measure of the relative amounts of products and reactants, when reaction is not at equilibrium
  • unlike the equilibrium constant, reaction quotient takes into consieration the concentration of reactants and products even when the reaction is not at equilibrium
  • gives an idea of what needs to occur to bring the reaction to equilibrium
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9
Q

If Q < Kc

State what happens for the following scenerio.

A
  • concentration of reactants is greater than the concentration of products
  • to bring the reaction to equilibrium, the reactants needs to be decreased
  • the foward reaction is favoured to bring reactionn to equilibrium
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10
Q

If Q > Kc

State what happens for the following scenerio.

A
  • concentration of products is greater than the concentration of reactants
  • concentration of products needs to be decreaesed to bring the reaction to equilibrium
  • the backward reaction is favoured to bring the reaction to equilibrium
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11
Q

If Q = Kc

State what happens for the following scenerio.

A
  • the reaction is at equilibrium
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12
Q

Le Chatelier’s Principle

A
  • the principal predicts how a reaction will respond to one or more changes and what direction the equilibrium will shift
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13
Q

According to Le Chatelier’s principle, what are the parameters that can influence the equilibrium of a reaction

A
  • temperature
  • catalyst
  • pressure
  • concentration
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14
Q

Le Chatelier’s principle

Temperature

Conditions if the enthalpy change (△H) of a system was positive.

A
  • positive enthalpy change means endothermic reaction
  • increase in temperature will result in the equilibrium shifting to the product side (or to the right) and the foward reaction will be favoured
  • decrease in temperature will result in the equilibrium shifting to the reactant side (or to the left) and the backward reaction will be favoured
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15
Q

Le Chatelier’s principle

Temperature

Conditions if the enthalpy change (△H) of a system was negative.

A
  • negative enthalpy change means exothermic reaction
  • increase in temperature will result in the equilibrium shifting to the reactant side and the backward reaction will be favoured
  • decrese in temperature will result in the equilibrium shifting to the product side (or to the right) and the foward reaction will be favoured
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16
Q

Le Chatelier’s principle

Catalyst

A
  • addition of catalyst increases the rate of the foward and backward reaction
  • position of equilibrium does not change
  • the equilibrium is attained faster
17
Q

Le Chatelier’s principle

Pressure

Number of gas molecules on the product side exceeds the reactant side.

A
  • increase in pressure leads to the equilibrium shifting to the reactant side (or to the left) and the backward reaction is favoured
  • decrease in pressure leads to the equilibrium shifting to the product side (or to the rigth) and the foward reaction is favoured
18
Q

Le Chatelier’s principle

Pressure

Number of gas molecules on the reactant side exceeds the product side.

A
  • Increase in pressure leads to the equilibrium shifting to the product side (or to the right) and the foward reaction is favoured
  • Decrease in pressure leads to the equilibrium shifting to the reactant side (or to the left) and the backward reaction is favoured
19
Q

Le Chatelier’s principle

Concentration

Concentration of reactants increase/concentration of products decrease.

A
  • Q < Kc
  • concentration of reactants needs to decrease
  • foward reaction is favoured
  • equilibrium shifts to the product side (or to the right)
20
Q

Le Chatelier’s principle

Concentration

Concentration of products increase/concentration of reactants decrease.

A
  • Q > Kc
  • concentration of products needs to decrease
  • backward reaction is favoured
  • equilibrium shifts to the reactant side (or to the left)
21
Q

Harber Process

A
  • N2(g)+3H2(g) ⇌ 2NH3(g)
  • enthalpy change is - 92 kJ/mol, therefore it is a exothermic reaction
  • the ammonia produced is used to make synthetic fertilizers, and in the synthesis of nitric acid , polymers and explosives
22
Q

Harber Process

To maximize the yeild of ammonia from this procees, what several condition need to be met?

A
  • low temperature
  • high pressure
  • concnetration of product
  • catalyst
23
Q

Harber Process

Low Temperature

A
  • exothermic reaction
  • product side will be favoured
  • optimum temperature of 450C is used because a lower temperature would slow down the rate of reaction
24
Q

Harber Process

High Pressure

A
  • the number of gas molecules on the product side is lesser than the number of gas molecules on the reactant side
  • foward reaction will be favoured
  • optimum pressure of **200 -250 ATM **is used as a high pressure would not be economically feasible
25
Q

Harber Process

Catalyst

A
  • solid iron (Fe) is used as the catalyst to speed up the rate of reaction and reach equilibrium faster
26
Q

Contact Process

A
  • 2SO2(g)+O2(g) ⇌ 2SO3(g)
  • enthalpy change of - 197 kJ/mol, therefore it is a exothermic reaction
  • the sulphuric acid (H2SO4), has many uses which include: fertilizers, dyes, soaps and detergents and paints and pigments.
27
Q

Contact Process

To maximize the yeild of sulfur trioxide from this procees, what several condition need to be met?

A
  • low temperature
  • high pressure
  • concentration of product
  • catalyst
28
Q

Contact Process

Low Temperature

A
  • exothermic reaction
  • product side is favoured
  • optimum temperature of 450C as a lower temperature would slow down the rate of reaction
29
Q

Conatct Process

High Pressure

A
  • the** # of gas molecules on the product side is lesser** than the # of gas molecules on the reactant side
  • foward reaction will be favoured
  • optimum pressure of 1 -2 ATM, this pressure is required in order to convert the reactants to products, the reaction is about 97% efficent at this pressure
30
Q

Contact Process

Concentration of Product

A
  • the sulfur trioxide that is produced is continuously being removed in order to shift the equilibroim to the right and favour the product side
31
Q

Contact Process

Catalyst

A
  • vanadium pentoxide (Va2O5) is used as a catalyst to speed up the rate of reaction and reach equilibrium faster

Chemistry (12 decks)

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