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acids and bases Flashcards

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1
Q

Define acids according to Arrhenius theory.

A

Substances that produce hydrogen ions (H+/H3O+/hydronium ions) in aqueous solution.

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2
Q

Define bases according to Arrhenius theory.

A

Substances that produce hydroxide ions (OH-) in aqueous solution.
Substances that react with H+(aq) to form a salt and water, with or without other products

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3
Q

What does the extension of the Arrhenius definition of a base result in?

A

Neutralisation reactions in aqueous medium to form salt and water

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4
Q

Limits of Arrhenius model

A
  1. Limits acids to substances soluble in water
  2. Limits acid-base reactions to aqueous solutions
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5
Q

Define a proton

A

The positive ion H+ derived from a H- atom by the removal of its electron

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6
Q

Define acids according to Lowry-Brønsted theory.

A

An acid is a proton (H+ ion) donor.

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7
Q

Define bases according to Lowry-Brønsted theory.

A

A base is a proton (H+ ion) acceptor.

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8
Q

Therefore, what happens in an acid-base reaction according to L-B model?

A

Proton(s) transferred from acid to base

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9
Q

What is the reaction as a result of L-B theory in practice and give definition for it

A

Protolysis is a reaction in which proton transfer takes place
L-B a-b reactions are protolytic

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10
Q

Define a conjugate acid-base pair

A

A reactant and a product that can be obtained from one another by the addition or removal of one proton (H+).

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11
Q

Define a conjugate acid

A

A conjugate acid in a conjugate acid-base pair is obtained from the base by addition of one proton (H+)

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12
Q

Define a conjugate base

A

A conjugate base in a conjugate acid-base pair is obtained from an acid by removal of one proton (H+)

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13
Q

What is a strong acid?

A

Acids that ionise completely in water to form a high concentration of H3O+ ions.

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14
Q

Examples of strong acids.

A

Hydrochloric acid, sulphuric acid, nitric acid (NHS)

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15
Q

What is a weak acid?

A

Acids that ionise incompletely in water to form a low concentration of H3O+ ions.

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16
Q

Examples of weak acids.

A

Ethanoic acid and oxalic acid

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17
Q

What is a strong base?

A

Bases that dissociate completely in water to form a high concentration of OH- ions.

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18
Q

Examples of strong bases

A

Sodium hydroxide and potassium hydroxide

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19
Q

What are weak bases?

A

Bases that dissociate incompletely in water to form a low concentration of OH- ions.

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20
Q

Examples of weak bases

A

Ammonia, calcium carbonate, potassium carbonate, calcium carbonate and sodium hydrogen carbonate

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21
Q

What is another distinction of acids and bases?

A

Concentrated and dilute

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22
Q

What is a concentrated acid/base?

A

Contain a large amount (number of moles) of acid/base in proportion to the volume of water

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23
Q

What is a dilute acid/base?

A

Contain a small amount (number of moles) of acid/base in proportion to the volume of water

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24
Q

Define ampholyte

A

A substance that can act as acid and base

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25
Q

Substances that are ampholytes are … or … substances

A

Amphiprotic
Amphoteric

26
Q

Examples of a ampholytes

A

Water
NH3
HSO4-
HCO3-

27
Q

Define proticity

A

The proticity of an acid is the number of protons that it can donate per formula unit

28
Q

Types of proticity

A

A monoprotic acid can donate “one” proton
Diprotic “two”
Triprotic “three”

29
Q

Acids that can donate more than one proton per formula unit

A

Polyprotic acids

30
Q

Define hydrolysis.

A

A reaction between a salt and water (formed from neutralisation) to form a solution that is acidic or basic

31
Q

What determines pH of solution of hydrolysis?

A

Relative strengths of acids and bases creating salt

32
Q

Hydrolysis of salt of weak acid and strong base produces

A

Alkaline (basic) solution where pH > 7

33
Q

Examples of salts from weak acid and strong base

A

Sodium ethanoate, sodium oxalate, sodium carbonate

34
Q

Hydrolysis of salt of strong acid and weak base

A

Acidic solution (pH < 7)

35
Q

Example of salt from strong acid and weak base

A

Ammonium chloride

36
Q

Salt of strong acid and strong base

A

Not undergo hydrolysis
Solution neutral (pH = 7)

37
Q

What reaction occurs as a result of amphoteric substances

A

Auto-ionisation / autoprotolysis / self-protolysis

38
Q

What is autoionisation?

A

Amphoteric substances donate protons that are accepted by another molecule of the same substance in the same liquid

39
Q

How do you write autoprotolysis in an equation?

A

Substance + substance > products
Or work from half reactions first to get net reaction

40
Q

What is a common occurrence of self-protolysis?

A

Water

41
Q

Chemical equilibrium (understanding not definition)

A

Net change of solution is 0 as forward and reverse reactions occurring at same rate

42
Q

When water autoionisation is at chemical equilibrium, we get

A

Pure water

43
Q

When an equation is at equilibrium

A

Double arrow

44
Q

Homogeneous reaction (understanding not learn)

A

States of matter of products and reactions same

45
Q

Heterogeneous reaction (understanding not learn)

A

One or more states within reaction differ

46
Q

Why is it important to understand the difference between homo and hetero exns?

A

Treated differently when calculating equilibrium constants - remember they deal with the “state” - HA - of the products and reactants when they are unchanging so we have to see what they’re like ykyk to see whats happening on a microscopic scale amirgiht or amiright

47
Q

So, what is an equilibrium constant?

A

Relationship between products and reactants of a reaction at equilibrium with respect to a specific unit (concentration or pressure) - i.e. how much of this and how much of that so that the forward and reverse rates of reaction are equal

48
Q

Therefore, what does the equilibrium constant consist of?

A

RATIO between units of products and reactants
Therefore it is a fraction

49
Q

Kw also known as…

A

Ionic product
Autoprotolytic constant
Dissociation constant

Of water

49
Q

Kw

A

[H3O+][OH-]

50
Q

What is the concentration of H3O+ and OH- in pure water (neutral)?

A

10-7

51
Q

Therefore… Kw =

A

10-14

52
Q

What is Kw used for?

A

CONSTANT value as baseline of all solutions at 25C regardless of acidity to see if more hydronium or hydroxide from acidity/alkalinity

53
Q

Solution neutral if

A

[H3O+] = [OH-] = 10-7

54
Q

Solution acidic if

A

[H3O+] > 10-7

55
Q

Solution basic if

A

[H3O+] < 10-7

56
Q

pH scale

A

1-6 : acid
7 : neutral
8-14 : base

57
Q

Where does pH scale come from?

A

Exponent of concentration of H3O+

58
Q

Therefore, what do we use to get pH?

A

Logs to isolate the exponent

59
Q

how to think of log laws

A

As exponents and their laws

60
Q

What is calculation to get pH

A

Log 1/[H3O+]
Bc exponent and put in denominator so negative exponent canceled when brought to top
-log [H3O+]
Other way to cancel negative

61
Q
A

Chemistry (4 decks)

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