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Chemistry module 5 > Equilibrium constant > Flashcards

Equilibrium constant Flashcards

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1
Q

What does a large number of Kc mean

A

further the position of equilibrium towards the products

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2
Q

What are the two types of equilibria

A
  • homogenous
  • heterogenous
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3
Q

What is homogenous equilibrium

A
  • contains equilibrium species that all have the same state or phase
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4
Q

What is heterogenou equilibrium

A
  • contains equilibrium specie that have different states or phases
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5
Q

What does homogenous equilbia Kc expression contain

A

concentrations of all species

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6
Q

What does the Kc expression of heterogenous equilibria contain and why

A
  • gases and aqueous only
  • as solids and liquids are essentially constant
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7
Q

What are the steps for figuring out Kc

A
  • work out equilibrium moles of all species
  • find equilibrium conctentrations
  • write expression for Kc and substitute vsalues
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8
Q

Describe the method to determine Kc

A
  • in a concical flask mix together 0.1mol of CH3COOH and o.1mol C2H5OH add 0.05 mol of HCL as an acid catalyst to the flask
  • the total volume of mixture in the flask is 20cm3
  • the amount of water in the aqueous acid catalyst is 0.5 mol
  • add 0.05 mol of HCL (aq) to a second conicall flask as a control
  • stopper both flasks and leave for a week to reach equilibrium
  • carry oit a titration on the equilibrium mixture using a standard solution of sodium hydroxidew
  • repeat the titration with the control to determine the amount of acid catlayst been acid
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9
Q

How are equilibrira involving gases expressed

A

in terms of Kp

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10
Q

What does Kp stand for

A

eqilibriu constant in terms of partial pressures

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11
Q

Decribe the relationship between concentration and pressure

A

proportional to one another

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12
Q

What is the mole fraction of a gas

A

is the same as its proportion by volume to the total volume of gases in a gas mixture

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13
Q

What is the formula for mole fraction

A
  • number of mols/total number of moles in gas mixture
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14
Q

What is partial pressure

A
  • contribution that the gas make towards the total pressure p
  • sum of partila pressures of each gas equals total pressure
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15
Q

What is the formula for partial pressure

A
  • mole fraction x total pressure
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16
Q

What are the three rules for the equilibrium position

A
  • if concentration of a species increases equilibrium position shifts in the direction that reduces the concentration
  • if the pressure is increaed the equilibrium poition shifts towards the side with fewer gasous moles
  • i the temperature is increased the equillibrium position shifts in the endothermic direction
17
Q

What does K=1 indicate

A

an equilibrium halfway between reactants and products

18
Q

What does K=100 indicate

A

an equilibrium well in favour of products

19
Q

What does K=0.01 indicate

A

equilibrium well in favour of reactants

20
Q

What does the value of K express

A

the exact position of equilibrium

21
Q

What happens to k at a set temperature

A

k is constant and does not change despite any modifications to concentration, pressure or the prescence of a catalyst

22
Q

Describe what happens to K af the temperature is changed

A

k does change
a temperature change is the only condition that will cause k to change it value

23
Q

What happens to equilibrium if the forward reaction is exothermic

A
  • the equilibrium constant decreases with increasing temperature
  • raising the temperature decreases the equilibrium yield of products
24
Q

Describe what hapens if the forward reaction is endothermic

A
  • the equilibriumm constant increases with increasing temperature
  • raising the temperature increases equilibriu m yield of products
25
Q

explain what happens when there are fewer moles of gasous products

A
  • ratio < k
  • When pressure increases:
  • products increase
  • reactants decrease
  • equilibrium shift right
26
Q

Describe what happens where there are more moles of gasoues products

A
  • ratio > k
  • when presssure increases:
  • products decrease
  • reactants increase
  • equilibrium shifts left
27
Q

Describe what happens when there are the same number of moles of gasoues reactans and products

A
  • ratio = k
  • no change in pressure
  • no effect of equilibrium shift
28
Q

Describe the effect of a catalyst on the affect of the equilibrium constant

A
  • equilibrium constants are unaffected by the prescence of a catalyst
  • catalysts affect the rate of a chemical reaction but not the position of equilibrium
29
Q

What does a catalyst do

A
  • speed up both forward and reverse reaction in equilibrium by the same factor
  • equilibrium is reached quicker but the equilibrium position is not changed

Chemistry module 5 (3 decks)

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