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Physical chemistry > Chemical Equilibria > Flashcards

Chemical Equilibria Flashcards

1
Q

What two things happen in a reversible reaction

A

• Forward and reverse reactions proceed at equal rates

• The concentrations of reactants and products remain constant

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2
Q

How does a catalyst affect affect the position of equilibrium?

A

It does not

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3
Q

What is the expression for Kc

A

Products/ reactants

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4
Q

Dynamic equilibrium is reached when:

A

• The rate of forward reaction is equal to the rate of backward reaction
• Concentration of both the products and reactants is constant

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5
Q

What factors alter the position of equilibrium?

A

• Temperature
• Pressure
• Concentration
• Amount of substance

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6
Q

What type of system does equilibrium take place in ?

A

A closed system

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7
Q

A bigger amount of products means what?

A

A bigger yield

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8
Q

Why don’t catalysts affect the position of equilibrium?

A

A catalyst provides an alternative pathway to lower the activation energy

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9
Q

What is le chataliers principle?

A

If a system (reversible reaction) is in equilibrium, if any condition is changed, the system will shift in such a direction to oppose the change and restore equilibrium

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10
Q

What does COSY stand for?

A

C- Change in conditions
O- Opposition to the change
S- Shift to oppose the change
Y- The equilibrium yield of the product

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11
Q

What equation is helpful in determining the effect of increasing/ decreasing temperature/pressure

A

N2 + 3H2 -> 2NH3(g) = -92 kj mol
<-

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12
Q

What is the effect of increasing the concentration of reactants on a reaction at equilibrium?

A

• Reactants increased
• Oppose the change
• Shift to RHS
• Yield increases

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13
Q

What is the effect of increasing the concentration of the products on a reaction at equilibrium

A

• Products increased
• Oppose the change in the products
• Shift to the left hand side
• The yield increases

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14
Q

What is the effect of removing the products from a reaction at equilibrium

A

• Product removed
•Oppose the change in productions
• Shift of equilibrium to the right hand side
• the yield will increase

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15
Q

What is the effect of increasing the pressure on a reaction at equilibrium

A

• Increase in pressure
• Oppose the increase in pressure
• Shift to the area with less moles
• either the yield will increase/decrease

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16
Q

What is the effect of decreasing the pressure on a reaction at equilibrium

A

• Decrease in pressure
• Oppose the decrease in pressure
• shifts to the area with more moles
• Either the products will increase or decrease

17
Q

What is the effect of increasing the temperature on an endothermic reaction at equilibrium

A

• Increase the temperature
• Oppose the increase in temperature
• Shifts to the right hand side
• Increase the yield

18
Q

What is the effect of decreasing the temperature on an endothermic reaction at equilibrium

A

• Decrease in temperature
• Oppose in decrease in temperature
• Shifts to the left hand side
• Decrease in the yield

19
Q

What is the effect of increasing the temperature on an exothermic reaction at equilibrium

A

• Increase in temperature
• Oppose in the increase in temperature
• Shift to the left hand side
• Decrease in yield

20
Q

What is the effect of decreasing the temperature on an exothermic reaction at equilibrium

A

• Decrease in temperature
• Oppose the decrease in temperature
• Shifts to the right hand side
• Increase in yield more products

21
Q

I’m industry, making the highest possible yield of products quickly and cheaply leads to a what?

A

Compromise between the reaction rate and chemical equilibrium

22
Q

What is the formula for Kc

A

Products/reactants

23
Q

How is Kc calculated?

A

Using Concentration of products and reactants

24
Q

What effect does increasing the pressure have on the rate of reaction?

A
  • Increasing the pressure will increase the rate of reaction
  • At a high pressure, there will be more oxygen molecules in a given volume/ the molecules will be pushed together
  • so, collision between the molecules is more likely
  • More collisions mean more successful and frequent collisions and a higher rate of reaction
25
Q

What is the effect of a catalyst on the number of molecules

A
  • increases the number of molecules able to react
  • lowers the activation energy by providing an alternative pathway
  • meaning that more molecules will have sufficient energy to react
26
Q

Give the units for the following reaction

• CH2=CH2(g) + H2O(g) equilibrium CH3CH2OH(g)

A

Mol-1dm3

Physical chemistry (10 decks)

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