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AH Chemistry > 2.1 chemical equilibrium > Flashcards

2.1 chemical equilibrium Flashcards

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1
Q

when is a chemical reaction in equilibrium

A

when the composition of the reactants and products remains constant indefinitely

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2
Q

what is K

A

the equilibrium constant

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3
Q

what does the equilibrium constant do

A

characterises the equilibrium composition of the reaction mixture

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4
Q

what are A, B, C, D in the equilibrium expression

A

the equilibrium concentrations

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5
Q

what are a,b,c,d in the equilibrium expression

A

the stoichiometric coefficients

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6
Q

can the value of K be calculated

A

yes

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7
Q

what does the value of K indicate

A

the position of the equilibrium

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8
Q

what are the units for K

A

there aren’t units for K

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9
Q

what are the concentrations of pure solids and pure liquids at equilibrium taken as

A

constant

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10
Q

what value are the concentrations of pure solids and liquids at equilibrium given in the equilibrium expression

A

1

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11
Q

what does the numerical value of K depend on

A

the reaction temperature

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12
Q

can K be altered by concentration and/or pressure

A

no

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13
Q

what happens to the value of K if the temperature is increased during an endothermic reaction

A

increase

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14
Q

what happens to the value of K if the temperature is decreased in an endothermic reaction

A

decrease

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15
Q

what happens to the value of K if the temperature is increased during an exothermic reaction

A

decrease

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16
Q

what happens to the value of K if the temperature is decreased in an exothermic reaction

A

increase

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17
Q

does the presence of a catalyst affect the value of the equilibrium constant

A

no

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18
Q

what is there an equilibrium between - in water and aq solutions

A

there is one between the water molecules and hydronium and hydroxide ions

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19
Q

what is the equation for the ionisation of water

A

H2O + H2O -> H3O+ + OH-

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20
Q

what is the chemical formula for a hydronium ion

A

H3O+

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21
Q

what is a hydronium ion

A

a hydrated proton

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22
Q

what does amphoteric mean

A

it can react as an acid and a base

23
Q

is water amphoteric? why can you conclude this?

A

yes, because it can react as an acid or as a base

24
Q

what is the dissociation constant for the ionisation of water known as? what is it represented by?

A

it is known as the ionic product and it is represented by Kw

25
Q

does the value of ionic product vary with temperature

A

yes

26
Q

what is the value of Kw at 25 degrees (approx)

A

1x10-14

27
Q

what is the Bronsted Lowry definition of acids and bases

A

an acid is a proton donor, and a base is proton acceptor

28
Q

what is formed by the loss of a proton, for every acid?

A

a conjugate base

29
Q

what is formed by the gain of a proton, for every base?

A

a conjugate acid

30
Q

which type of acids and bases are completely dissociated into ions in aqueous solution

A

strong

31
Q

which type of acids and bases are only partially dissociated into ions in aqueous solutions

A

weak

32
Q

what are some examples of strong acids

A
  • hydrochloric acid
  • sulfuric acid
  • nitric acid
33
Q

what are examples of weak acids

A
  • ethanoic acid
  • carbonic acid
  • sulfurous acid
34
Q

what is an example of a strong base

A

solutions of metal hydroxides (eg sodium hydroxide)

35
Q

what are examples of weak bases

A

ammonia and amines

36
Q

how can the weakly acidic nature of some substances be explained

A

reference to the equations showing the equilibria

37
Q

what are the differences between the equimolar solutions of weak and strong acids

A
  • pH values
  • conductivity
  • reaction rates
38
Q

what are the similarities between equimolar solutions of weak and strong acids

A

the stoichiometry of reactions are the same

39
Q

what two acids and bases dissolve in water to produce neutral solutions

A
  • strong acid and strong base
  • weak acid and weak base
40
Q

which acid and base dissolve in water to produce an alkaline solution

A
  • weak acid and strong base
41
Q

which acid and base dissolve in water to produce an acidic solution

A

strong acid and weak base

42
Q

what does the name of the salt produced depend on

A

the acid and base used

43
Q

what is a buffer solution

A

one in which the pH remains approx constant when small amounts of acid, base or water are added

44
Q

what does an acid buffer consist of

A

a solution of a weak acid and one of its salts made from a strong base

45
Q

what occurs in an acid buffer when a small amount of base is added

A

the weak acid provides hydrogen ions when these are removed by the addition of a small amount of base

46
Q

what occurs in a basic buffer when an acid is added

A

the weak base removes excess hydrogen ions

47
Q

how can an approx pH of an acid buffer solution be calculated

A

from its composition and from the acid dissociation constant

48
Q

what are indicators

A

weak acids

49
Q

what does Kin represent

A

the acid indicator dissociation

50
Q

when in the colour of an acid indicator distinctly different from that of its conjugate base

A

in aqueous solution

51
Q

when can the colour change of an indicator assumed to be distinguishable

A

when [HIn] and [In-] differ by a factor of 10

52
Q

how can suitable indicators be selected

A

from pH data, including titration curves

53
Q

what occurs in a basic buffer when a small amount of base is added

A

the conjugate acid provided by the salt supplies hydrogen ions when these are removed by the addition of the base

54
Q

what occurs in an acidic buffer when a small amount of acid is added

A

the salt of the weak acid provides the conjugate base which can absorb excess hydrogen ions produced by the addition of a small amount of base

AH Chemistry (35 decks)

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