chemical equilibria Flashcards

1
Q

how is it often denoted that a reaction is reversible

A

using a double headed arrow

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2
Q

where can an equilibrium only be established

A

in a closed system

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3
Q

where can equilibrium be set up from

A

either direction

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4
Q

what is reached at equilibrium

A

a natural balance between products and reactants

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5
Q

why are chemical equilibria dynamic

A

both the forward and reverse reactions continue to occur

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6
Q

rate of forward reaction equals…

A

rate of reverse reaction

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7
Q

the concentrations of reactants and products remain constant unless…

A

the conditions are changed

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8
Q

what can changes to the conditions of an equilibrium affect

A

the position of the equilibrium

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9
Q

le chateliers principle

A

if a system in equilibrium is subjected to change, the position of the equilibrium will move in the direction which opposes that change

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10
Q

when will the equilibrium shift to the right

A

if the conc of reactant is increased/conc of product decreased

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11
Q

when will the equilibrium shift to the left

A

if the conc of reactant in decreased/conc of product increased

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12
Q

which side does the equilibrium shift to if the total pressure is increased

A

to the side with fewer moles of gas because fewer moles of gas exert less pressure

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13
Q

which side does the equilibrium shift to if the total pressure is decreased

A

to the side with more moles of gas because more moles of gas exert more pressure

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14
Q

what effect does an increase in pressure have on the rate of reaction

A

increases rate of reaction

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15
Q

why does increased pressure increase rate of reaction

A

collisions between molecules are more frequent

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16
Q

which direction will the equilibrium move in if the temp is increased

A

the direction of the endothermic reaction (TAKES HEAT IN)

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17
Q

which direction will the equilibrium move in if the temperature is decreased

A

the direction of the exothermic reaction (GIVES OUT HEAT)

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18
Q

what does the way the equilibrium responds to change in temperature depend on

A

whether the forward reaction is exothermic or endothermic

19
Q

what does an increase in temperature always increase

A

the rate of the forward and backward reactions but to different extents

20
Q

what does a catalyst increase the rate of the forward and backward reactions by

A

the same amount

21
Q

what effect does a catalyst have on the equilibrium position/yield

A

none

22
Q

what does using a catalyst increase

A

the rate at which the equilibrium position is reached

23
Q

the haber process

A

N2(g)+3H2(g)> 2NH3 (g)

24
Q

what is dependent on the conditions used in the haber process

A

the equilibrium position, yield of ammonia and rate of reaction

25
Q

what are used in order to balance yield of ammonia, rate of ammonia production and energy requirements

A

a compromise temperature and pressure

26
Q

what pressure is the haber process conducted under

A

200 atm

27
Q

what temperature is the haber process conducted under

A

400-450 degrees celcius

28
Q

what catalyst is used in the haber process

A

iron

29
Q

what is also used in the haber process

A

recycling

30
Q

what is Kc

A

the equilibrium constant in terms of the concentrations of the reactants and products

31
Q

Kc=

A

aA + bB >< cC + dD

(C)c(D)d- PRODUCTS/(A)a(B)b- REACTANTS

32
Q

what are (A) (B) (C) (D)

A

the concentrations of the reactants and products at equilibrium

33
Q

what are a b c and d

A

the stoichiometric coefficients of the balanced equation (moles)

34
Q

what does the value of Kc indicate

A

the extent of the reaction

35
Q

what does it mean if Kc is less than one

A

there are more reactants than products, equilibrium lies to left hand side

36
Q

what does it mean if Kc is equal to one

A

reactants = products

37
Q

what does it mean if Kc is greater than one

A

there are more products than reactants so the equilibrium lies to the left hand side

38
Q

what do the units for Kc depend on

A

the reaction, must be determined for each Kc expression

39
Q

does the presence of a catalyst or change in concentration affect Kc

A

no

40
Q

what does affect Kc

A

change in temperature

41
Q

what will happen to Kc if the temperature change causes the equilibrium to shift right

A

Kc will increase

42
Q

what will happen to Kc if temperature change causes equilibrium to shift left

A

Kc will decrease

43
Q

what will there be a mixture of when a reversible reaction has reached equilibrium

A

reactants and products

44
Q

what can the amount of each chemical present at equilibrium be determined by

A

the balanced equation and the initial moles