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CHEM1602 > Chapter 16: Acids and Bases > Flashcards

Chapter 16: Acids and Bases Flashcards

1
Q

What is the Arrhenius definition of an acid?

A

A substance that produces H+ ions in aqueous solution.

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2
Q

What is the Arrhenius definition of a base?

A

A substance that produces OH- ions in aqueous solution.

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3
Q

What does the strength of an acid or a base depend on?

A

The extent of the electrolyte’s dissociation into its component ions.

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4
Q

What is a strong acid?

A

An acid that completely dissociates (ionizes) in solution.

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5
Q

What is a weak acid?

A

An acid that partially dissociates (ionizes) in solution.

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6
Q

What is a strong base?

A

A base that completely dissociates (ionizes) in solution.

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7
Q

What is a weak base?

A

A base that partially dissociates (ionizes) in solution.

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8
Q

What is the Bronsted-Lowry definition of an acid?

A

A proton (H+) donor.

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9
Q

What is the Bronsted-Lowry definition of a base?

A

A proton (H+) acceptor.

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10
Q

What are amphoteric substances?

A

Substances that can act as acids or bases.

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11
Q

What is a conjugate acid-base pair?

A

Two substances related to each other by the transfer of a proton.

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12
Q

What is a conjugate acid?

A

Any base to which a proton has been added.

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13
Q

What is a conjugate base?

A

Any acid from which a proton has been removed.

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14
Q

What are the factors of a molecule that affect the ease with which a hydrogen is donated (and therefore makes the molecule acidic)?

A
  1. The polarity of the bond
  2. The strength of the bond
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15
Q

In order for HY to be acidic, the H–Y bond must be what?

A

The H–Y bond must be polarized with the hydrogen atom as the positive pole because hydrogen must be lost from the acid as a positively charged ion. A partial positive charge on the hydrogen atom facilitates its loss.

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16
Q

Why isn’t LiH acidic?

A

It is ionic with the negative charge on the hydrogen atom. (H is more electronegative than Li)

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17
Q

Why isn’t the C–H bond acidic?

A

It is virtually nonpolar because the electronegativities of carbon and hydrogen are similar; therefore, C–H is not acidic.

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18
Q

Why is the H–F bond acidic?

A

The H–F bond is polar with the positive charge on the hydrogen atom.

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19
Q

How does the strength of the H–Y bond relate to the strength of an acid? Why?

A

The stronger the H–Y bond, the weaker the acid. The more tightly the hydrogen atom is held, the less likely it is to come off.

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20
Q

Why are HCl and HBr strong acids but HF is not?

A

HCl and HBr have weaker bonds. HF, in contrast, has a stronger bond and is therefore a weak acid, despite the greater bond polarity of HF.

21
Q

In oxyacids, what determines the ease with which the H is donated?

A

The ease with which the H is donated is related to the strength and polarity of the H–O bond. The factors affecting the strength and polarity of the bond are the electronegativity of the element Y and the number of oxygen atoms attached to the element Y.

22
Q

As Y becomes more electronegative, how does this affect the H–O bond of an oxyacid?

A

The more electronegative the element Y is, the more it weakens and polarizes the H–O bond and the more acidic the oxyacid is.

23
Q

How does the number of oxygen atoms bonded to Y affect the strength of the acid?

A

The greater the number of oxygen atoms bonded to Y, the stronger the acid.

24
Q

What are the six strong acids given in the book?

A
  1. HCl (hydrochloric acid)
  2. HBr (hydrobromic acid)
  3. HI (hydroiodic acid)
  4. HNO3 (nitric acid)
  5. HClO4 (perchloric acid)
  6. H2SO4 (sulfuric acid)
25
Q

Why is HCl a strong acid but HF is not?

A

The strength of the HF bond relative to the HCl bond makes HF less likely to ionize in solution than HCl.

26
Q

What is the acid ionization constant (Ka)?

A

The equilibrium constant for the ionization reaction of the weak acid in water. It is a way to quantify the relative strength of a weak acid.

27
Q

What is the autoionization of water?

A

When water acts as an acid and a base with itself. Given by the reaction: H2O <=> H+ + OH-

28
Q

What is the ion product constant of water?

A

[H+][OH-] = 10^-14 at 25˚ C

29
Q

How is pH defined?

A

pH is the negative of the log of the hydronium ion concentration. pH = -log[H3O+]

30
Q

How is pOH defined?

A

pOH = -log[OH-]

31
Q

How are pH and pOH related to each other?

A

They add to 14.00 at 25˚ C.

32
Q

How is pKa defined?

A

pKa = -log(Ka)

33
Q

How is pKa used to quantify the strength of an acid?

A

The smaller the pKa, the stronger the acid.

34
Q

In a solution containing a strong or weak acid, what are the two potential sources of H3O+?

A
  1. The ionization of the acid
  2. The autoionization of water
35
Q

What is the percent ionization of a weak acid?

A

The ratio of the ionized acid concentration to the initial acid concentration, multiplied by 100%.

36
Q

How is the equilibrium H3O+ concentration of a weak acid related to its initial concentration?

A

The equilibrium H+ concentration increases with increasing initial concentration of the acid.

37
Q

How is the percent ionization of a weak acid related to its concentration?

A

The percent ionization of a weak acid decreases with increasing concentration of the acid.

38
Q

When a strong acid and a weak acid are in solution, what effect does the strong acid have on the weak acid?

A

The H+ formed by the strong acid suppresses the formation of additional H+ by the weak acid or the autoionization of water.

39
Q

What is the base ionization constant (Kb)?

A

The extent of ionization of a weak base in solution. Given by: Kb = [BH+][OH-]/[B]

40
Q

An anion that is the conjugate base of a weak acid is what?

A

A weak base.

41
Q

An anion that is the conjugate base of a strong acid is what?

A

pH-neutral (forms solutions that are neither acidic nor basic)

42
Q

How is the strength of an acid related to the strength of its conjugate base?

A

The weaker the acid, the stronger the conjugate base.

43
Q

pKa + pKb = ?

A

14

44
Q

How do anions and cations factor into acid-base reactions?

A

Anions can sometimes act as weak bases. Cation can sometimes act as weak acids.

45
Q

In general, cations that are the counterions of strong bases are what?

A

pH-neutral. For example, Na+, K+, and Ca2+ are the counterions of the strong bases NaOH, KOH, and Ca(OH)2 and are therefore themselves pH-neutral.

46
Q

In general, a cation that is the conjugate acid of a weak base is what?

A

A weak acid.

47
Q

What effect do small, highly charged metal cations have in solution?

A

Cations such as Al3+ and Fe3+ form weakly acidic solutions.

48
Q

What is the definition of a Lewis acid?

A

An electron pair acceptor.

49
Q

What is the definition of a Lewis base?

A

An electron pair donor.

CHEM1602 (8 decks)

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