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Introductory Chemistry Flashcards > Chemical Equilibrium > Flashcards

Chemical Equilibrium Flashcards

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1
Q

Define collusion theory

A

States that for a reaction to occur, particles must collide at a suitable orientation, and with energy greater than or equal to the activation energy, therefore allowing new bonds t be formed and old bonds to broken during the transition state.

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1
Q

define activation energy

A

The different in energy between the reactant particles and the activated transition state.

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2
Q

Define transition state

A

The point of highest potential energy during the reaction. hence it is extremely unstable, and quickly shifts to lead to the formation of either the products or the reactants.

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3
Q

Define reaction rate

A

The number of successful collisions in a given time (i.e. the rate at which reactants form products), thus the greater number of successful collusion, the faster the reaction proceeds.

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4
Q

What are the 6 factors affecting reaction rate.

A
  • concentration
  • pressure
  • temperature
  • surface area/state of subdivision
  • catalysts
  • nature of the reactants
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5
Q

Draw a graph explaining the reaction progress, energy and the transition state.

A

see page 2

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6
Q

Explain how concentration affects reaction rates

A

if the concentreation of a particular speices is increased, then the number of paerticles in a given volume will be increased so more successful collisions can occur

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7
Q

Explain how pressure affects reaction rates

A

gas pressure is caused by the force of particules colliding with the walls of a container, thus if pressure is increased it means there are more gaseous particules in a given volume, and more successful collusions can take place.

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8
Q

explain how temperature affects reaction rates

A

increased tempreature means an increase in paerticule kinetic energy. the particles have greater energy to supply collusions, meaning more collusions occur with sufficent energy to overcome the transition state. they alose have a greater velocity, so collsuions occur more frequently

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9
Q

explain how surface area/state of subdivision affects reaction rates

A

a solid can only expoise it enterior partivcles for collisions, thus when a solid is crushed or divided, more particles are exposed for collusions.

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10
Q

explain how catalysts affects reaction rates

A

a catalyst interacts with the reactants to provide an alternative reaction pathway with a lower activation energy, thus more particles have sufficient energy in a collision to match or exceed the activation energy.

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11
Q

explain how nature of the reactants affects reaction rates

A

the number and type of bonds to be broken affects the rate of reaction, as it determines the amount of energy needed to convert the reactants to products. recall that the breaking of bonds requires energy input, while the formation of bonds releases energy.

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12
Q

what is a reversible reaction

A

the reactants form the product, which can. them reform the reactants.

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13
Q

what is required for a reversible reaction

A

the activation energy fro both the forward and reverse reaction must be relatively low, so sufficent partucle withh ahbe enough enrrgy for a succesdful collision for both reactions.

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14
Q

what makes a reaction non-reversable

A

if the activation enerfgy for the reverse reaction os signicantly higher than that of the forward reaction, the products do not react to reform the reactions. also note that all physical changes can be reversed, while only some chemcial changes are reversible.

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15
Q

draw a graph explaijning the relatiknship between energy and reaction process in non-reversable reactions

A

see page 3

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16
Q

what is a dynamic equilibrium

A

in a reversible reaction, the reaction is never reacthing complition, it produces a state of dynamic equilibirum where the rate of the reverse and forward reactions are the same, and the concentrations of reactions and products remain constant.

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17
Q

what forms a system

A

chemicals involved in a reaction

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18
Q

what are the surroundings of a reaction

A

anything immediate to the reaction but isn’t involved in the reaction itself.

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19
Q

what is a open system

A

both matter and energy are able to leave the system

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20
Q

what is a closed system

A

only energy can leave the system

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21
Q

what is required for an equilibrium to be reached and maintained.

A

no matter is permitted to leave, so a closed system is required.

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22
Q

what are physical changes

A

don’t produce any new substances, these only change the physical properties of the reacting substances (e.g. a state change) (note that chemical systems can involve both physical and chemical changes)

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23
Q

what are chemical changes

A

produces new substances from the reacting ones, these have new chemicial properties. these are usually accompanied by some energy change, due to the rearrangement f bonds required of form a new chemical species.

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24
Q

when is a equilibrium reached

A

1) reactants first placed in closed chemical system = concentration of reactants is much higher than concentration of the products (reverse reaction can’t occur)

2) as reaction continues = concentration of the products increases until they in greater conc. than the reactants.

3) reaction then proceeds in a reverse direction = reverse directtion contineues until both reactions are proceeding at the same rate, hence no change occurs withhin the system.

when this point is reached, the system is said to be in equilibrium.

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25
Q

what are the three defining characteristics or equilitbriums

A

1) reaction rate: equilibrium requires the opposing reactions to occur at the same rate

2) concentration: the concentrations of reactants and products remains constant

3) macroscopic properties: the macroscopic properties of the system are the properties that are obvious enough to see/measure directly (colour, temperautre etc) also remain constant.

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26
Q

what does le chateliers principle do

A

predicts the way in which a system reacts to a change

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27
Q

what is le chateliers principle

A

“if a system at equilibrium is subject to a change in conditions, then the system will behave in such a way as to partially counteract that change and establish a new equilibrium”

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28
Q

what are the changes imposed on a system that urge le chaeliers principle to occur?

A

temperature
concentration
total pressure (gaseous system)

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29
Q

what is an exothermic reaction

A

the reactants have more energy than the products, hence it cools the system

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30
Q

what is an endothermic reaction

A

this heats the system as the products have greater energy than the reactants.

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31
Q

what does an increase in temperature favour in an equilibrium

A

an increase in temperature favours the endothermic reaction as it converts the added kinetic energy into chemical potential energy (causing the formation of chemical bonds) thus reducing the temp. of system.

32
Q

what does a decrease in temperature favour in an equilibrium

A

a decrease in temperature favours the exothermic reaction as it converts chemical potential energy to kinetic energy (causing the breaking of chemical bonds to release heat) thus raising the temp. of the system.

33
Q

what is enthalpy

A
34
Q

what does lower enthalpy of the reactants in an endothermic reaction mean

A

that the endothermic reaction has a greater activation energy than the exothermic reaction for the same reversible reaction.

35
Q

what does an increase in temperature result in

A

increases the rates of both reactions but affects the endothermic reaction more, since it means a significantly greater proportion of particle can react in the endothermic reaction due to high activation. this will raise rate of exothermic reaction and so on until equilibrium is re-established in new position.

36
Q

what does a decrease in temperature do?

A

slows the endothermic reaction more, thus the exothermic reaction is faster, the endothermic reaction gradually increases in rate until equilibrium is re-estrablished.

(keep in mind that while this explains how equilibrium is reattained, it is not rate that drives an equilibrium change.

37
Q

what is a species in chemistry

A
38
Q

what happens when a species in solution increases in concentration

A

equilirbrium shifts to favour the reaction that will consume the added specuies thereby decreasing its concentration.

39
Q

what happens when a species in solution decreases in concentration

A

equilibrium will shift to favour the reaction that will produce more of the ddepletred species, increasing its concentration.

40
Q

how can a species concentration be increased

A

addition of more of that species to the system

41
Q

how can a species concentration be decreased

A

adding a substance what will either react with the species to produce one of the products, or that will react with the species to form a precipitate.

42
Q

in terms of collision theory and reaction rate, if the concentration of a species in a chemical system is increased, what happens

A

then the reaction that consumes that species will increase in rate, to remove the additional species, this continues until equilibrium is re-established when the rates become equal and the concentrations are constant.

43
Q

in terms of collision theory and reaction rate, if the concentration of a species in a chemical system is decreased, what happens

A

the reaction that produces that species increases in rate to replenish the depleted species.

44
Q
A

in an aqueous solution, a change in volume corresponds to the addition or removal of water (dilution/concentration). this will decrease of increase the concentrations of all species and (depending on mole ratio and reaction rates) equilibrium will shift to increase or decrease the volume.

45
Q
A

increasing or decreasing the partial pressure of a gas (exerted by a single gaseous species in a system) can be considered a way of increasing/ decreasing the conc. of that species, so the system reacts in much the same way as it would to a change in, and equilibrium will shift to consume or produce a particuke species.

46
Q

in gasous system, what does a increase or decrease in volume do

A

corresponds to a change in pressure, partial pressure can also be altered by the addition of one of the gaseous species present in the system.

47
Q
A

when pressure changes, the system will favour the reaction that will increase or decrease the total pressure to restore it to the equilibrium pressure.

48
Q
A

this depends on the mole ratio of species on both sides of the balanced chemical equation.

49
Q
A

an increase in pressure favours the side with fewer moles of gaseous species since it’ll decrease the pressure, while a decrease in pressure favour the reaction that produces a greater number of moles of gas as this acts to increase the pressure.

50
Q
A

if boths sides have the same ratio of gaseous species, then there will be no changes to equilirbrium, as there is no change to reaction reate.

51
Q

in terms of collision theory/reaction rates.

A

changes to volume and pressure cause alterations to concentration of all the species in the system, thus both reactions change in rate.

If one side of the reaction has a greater molar proportion of gaseous species, then that side has a greater increase/decrease in reaction rate.

however equilibrium will be re-established when the rates of the reactions are equal and concentrations remain constant.

52
Q
A

no effect is mae on equilibrium if an inert gas is added, as no partial pressures are altered (the added gas must be one present in the system, or one that will reaction with a gas in the system).

53
Q

what is a catalyst considered as in a system and why is this important.

A

can be considered as part of the surroundings rather than a part of the system, because it remains unchanged by the proceeding reaction.

thus, a catalyst can increase the rate at which equilibrium is obtained, but it doesn’t affect the position of equilibrium itself.

54
Q

what is a catalyst

A

a catalyst is used to interact with the reactants of a system and provide an alternative pathway (form intermediate compounds) with a lower activation energy and thus allow for a faster reaction rate.

55
Q

what is the equilibrium expression?

A

indicates the extent to which a reaction goes to completion qualitatively, this can be used ot determine the equilibrium constant (K_c). it is determined for a specifci reaction at a given temperature

56
Q

what does K_c represent

A

represents the ratio of products and reactants at equilibrium.

the re;ative proportions of reactants and products indicates the extent to which the reaction has progresed and thus indicates the poisiton of equilbrium (whether forward or reverse reaction is favoured in particular system)

57
Q
A

when a change is imposed on chemical system in equilibrium, accourding LCP the system behaves in such a way that partially counteracts the imposed change. in this way, equilibrium is re-established for the same equilibrium constant (K)

58
Q

what is the formula for equilibrium constant (K) and equilibrium constant (i think lol idfk cunt)

A

see page 6

59
Q

what is homologous system

A

system constists of species of the same state

60
Q

what is heterologous system

A

and a heterologous system involves species of different states.

keep in mind that solutions and gases vary in concentration and thus are added into the equation; however, solids and liquids are of fixed concentration ad thus are not involved.

61
Q

what does change in temperature affect?

A

proportion of particles with sufficient energy to react for each reaction. so ratio of reactants to products will depend on temperature, so any change in temperature beings about a change in the equilibrium constant for a reaction.

62
Q

what si the equilibrium constant

A

a quantitative way of determinigj the “poisiton’ of equilibrium. when talking about poistion of equilibirum, we are interested in which reaction (forward or reverse) is favoured, so whether more reactants or products exist in system once equilibrium has been reached.

63
Q

if the K value is >1, then ______

A

the forward reaxction is favoured as there is a greater proportion of products than reactants

64
Q

if the K value is <1, then ______

A

the reverse reaction isa favoured as there is a greater proportion of reactants than products.

65
Q

if the K value is =1, then ______

A

they’re approximately of equal concentration and equilibrium doesn’t significantly favour either side.

66
Q
A

the reaction quotient (Q_c) is determined with the same formula as the equilibrium constant, however the system is not necessarily at equilibrium. if Q = K then the system is at equilibrium.

67
Q

in terms of graphs, number of lines for concentration vs time

A

any number, depending on the number of products and reactants

68
Q

in terms of graphs, number of lines for reaction rates vs time

A

two (forward and reverse reactions)

69
Q

in terms of graphs, position of line at equilibrium for concentration vs time

A

All lines plateau as concentrations are constant (though not necessarily of equal value)

70
Q

in terms of graphs, position of line at equilibrium for reaction rates vs time

A

two lines meet and plateau as rates are equal and constant.

71
Q

key features of an increase in concentration/ partial pressure of one substance on a graph

A

sudden increase in one substance

72
Q

key features of an decrease in concentration/ partial pressure of one substance on a graph

A

sudden decrease in one substance

73
Q

key features of an increase in volume/ decrease in pressure on a graph

A

sudden decrease in all gaseous species

74
Q

key features of an decrease in volume/ increase in pressure on a graph

A

sudden increase in all gaseous species

75
Q

key features of an increase in temperature on a graph

A

no sudden changes

76
Q

key features of an decrease in temperature on a graph

A

no sudden changes

77
Q

why are mole ratios of species in a system

A

this will affect the slope of the lines in the graph

Introductory Chemistry Flashcards (15 decks)

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