Chemical Equilibria Flashcards

1
Q

When is a chemical reaction in dynamic equilibrium?

A

When the rate of the forward reaction and reverse reaction is equal.

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2
Q

What is the equilibrium constant?

A

It characterises the equilibrium composition of the reaction mixture.

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3
Q

What is the general equation of the equilibrium constant?

A

aA +bB >< cC + dD

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4
Q

What is the equilibrium expression?

A

K = (C)^c(D)^d/(A)^a(B)^b

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5
Q

What is homogenous equilibria?

A

Where all the substances are in the same phase.

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6
Q

What is heterogeneous equilibria?

A

Where the substances are in different phases

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7
Q

What is the concentration of pure solids and pure liquids at equilibrium?

A

Taken as a constant value of one in the equilibrium expression.

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8
Q

What does the numerical value of the equilibrium constant depend on?

A

Only on the reaction temperature and independent of the concentration and/or pressure.

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9
Q

What happens to the equilibrium constant (K) value in exothermic reactions?

A

A rise in temperature causes a decrease in the K value and the yield of product is decreased.

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10
Q

What happens to the equilibrium constant (K) value in endothermic reactions?

A

A rise in the temperature results in an increase in the K value and the yield of product is increased.

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11
Q

What happens to the equilibrium constant value in the presence of a catalyst.

A

The presence of a catalyst does not affect the value of the equilibrium constant.

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12
Q

What is the equation of the ionisation of water?

A

2H2O><H3O^+ + OH^-

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13
Q

What is a hydronium ion?

A

H3O^+ represents a hydronium ions, a hydrated proton.

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14
Q

What is amphoteric and give example of a substance that is.

A

Amphoteric is a substance that can act as an acid and base and an example of this is water.

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15
Q

What is the dissociation constant of water?

A

Known as the ionic product and is Kw = (H3O^+)(OH^-)

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16
Q

What is the value of the dissociation constant of water?

A

25^oC is 1 x 10^-1

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17
Q

What is the relationship between the hydrogen ion concentration and pH?

A

pH = -log(H^+) and (H^+) = 10^-pH

18
Q

What is the relationship between pH and pOH?

A

pH + pOH = 14

19
Q

What is monoprotic?

A

Monoprotic is when only one proton (H^+) is formed e.g. HCl

20
Q

What is diprotic?

A

Diprotic is when two protons are formed e.g. H2SO4

21
Q

What is triprotic?

A

Triprotic is when three protons are formed e.g. H3PO4

22
Q

What are the Bronsted- Lowry definitions of acids and bases?

A

Acids are proton donors and bases are proton acceptors.

23
Q

What does the acid form?

A

For every acid there is a conjugate base, formed by the loss of a proton.

24
Q

What does the base form?

A

For every base there is a conjugate acid, formed by the gain of a proton

25
Q

What are strong acids and bases?

A

Those that completely ionise (dissociate) into ions when dissolved in water.

26
Q

What are some examples of strong acids and bases?

A

Acids include hydrochloric, sulfuric and nitric acid
Bases include metal hydroxides

27
Q

What are weak acids and bases?

A

Partially ionised (dissociated) when dissolved in water.

28
Q

What are some examples of weak acids and bases?

A

Acids include Ethanoic acid, carbonic acid and sulfurous acid
Bases include Ammonia and amines

29
Q

What are the properties of a strong acid?

A

High conductivity, Fast reaction rate, lower pH and same volume to neutralise alkali.

30
Q

What are the properties of a weak acid?

A

Lower conductivity, lower rate of reaction, higher pH and same volume to neutralise alkali.

31
Q

What is the acid dissociation constant?

A

Ka = (H3O^+)(A^-)/(HA)

32
Q

What does a soluble salt of a strong acid and a strong base dissolves in water produce?

A

A neutral solution

33
Q

What does soluble salt of a weak acid and a strong base dissolves in water to produce?

A

A alkaline solution

34
Q

What does a soluble salt of a strong acid and a weak base dissolves in water to produce?

A

An acidic solution

35
Q

What is a buffer solution?

A

One that resists a change in pH when moderate amounts of an acid or base added to it.

36
Q

What does an acidic buffer consist of?

A

a Solution of a weak acid and a salt from a strong base

37
Q

What happens to a buffer in the addition of an acid?

A

In an acid buffer solution the weak acid provides hydrogen ions when
these are removed by the addition of a small amount of base. 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
acid.

38
Q

What is a basic buffer?

A

Consists of a solution of a weak base and a salt from a strong acid.

39
Q

What happens to a buffer in the addition of an acid?

A

In a basic buffer solution the weak base removes excess hydrogen
ions, and the conjugate acid provided by the salt supplies hydrogen
ions when these are removed

40
Q

What are indicators?

A

They are used in acid-base titrations as they change colour at the end-point of the reaction

41
Q

How is the colour of the indicator determined?

A

Determined by the ration of (In^-) : (HIn)

42
Q

When is colour of indicator distinguishable?

A

The colour change is assumed to be distinguishable when
(HIn) and (In^-) differ by a factor of 10.