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CHM2046 > Topic 18 - Acids / Bases > Flashcards

Topic 18 - Acids / Bases Flashcards

1
Q

Arrhenius acid definition

A

Substance with covalently bonded H atoms and dissociates in H2O to yield H3O+

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2
Q

Arrhenius base definition

A

Substances with OH in its formula that dissociates in H2O to yield OH

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3
Q

Arrehenius Acid-Base Reaction

A

Neutralization
a) Exothermic (-55.9 kJ mol-)
b) Formation of H2O (l) and salt

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4
Q

Strength of an acid / base

A

Extent of dissociation to produce [H+] and [OH−] in solution

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5
Q

Strong acid / base

A

Fully dissociate in solution (~100%)

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6
Q

Weak acid / base

A

Partially dissociate in solution (<5%)

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7
Q

Substances that behave as strong acids

A

HNO3
HCl
HBr
HI
H2SO4
HClO3
HClO4

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8
Q

Substances that behave as weak acids

A

a) HF
b) Oxoacids (# O atoms = > ionizable H+)
c) H is not bonded to O or to a halogen
d) Carboxylic acids (ROOCH)

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9
Q

Substances that behave as strong bases

A

Water soluble compounds containing OH- or O2-
a) G1
b) G2 (except Mg)

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10
Q

Substances that behave as weak bases

A

a) Those with an e- rich N atoms (Ammonia / Amines)
b) Anions of weak acids

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11
Q

Acid dissociation constant (Ka)

A

Measures the extent of acid dissociation in water

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12
Q

Water Autoionization Formula

A

2H2O(l)⇌H3O+(𝑎𝑞 )+OH−(𝑎𝑞 )

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13
Q

Reasons for Water Autoionization

A

Amphoteric nature of H2O

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14
Q

Ion-product constant of H2O (at 298K)

A

Kw = [H+][OH−] = 1.0×10−14

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15
Q

Relationship between H3O+ and OH-

A

Inversely proportional
a) As the concentration of one of these ions increases, the concentration of the other must decrease

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16
Q

When is a solution…?
a) Neutral
b) Basic
c) Acidic

A

a) H+ = OH-
b) H+ < OH-
c) H+ > OH-

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17
Q

pH

A

-log([H+])

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18
Q

Number of significant figures inside the logarithm should equal…

A

the number of decimal places in the number

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19
Q

pH + pOH = … (at 298K)

A

14

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20
Q

How is pH measured?

A

a) Acid-base indicators. Organic molecules where color depends on the solution’s acidity
b) pH meter (Probe with 2 electrodes)

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21
Q

Bronsted-Lowry acid definition

A

Proton donor

22
Q

Bronsted-Lowry base definition

A

Proton acceptor containing a lone pair of e-

23
Q

Brønsted-Lowry Acid-Base Reaction

A

Proton transfer process that can occur between gases, nonaqueous solutions, and heterogeneous mixture

24
Q

Conjugate acid-base pairs

A

Two species which differ by H+
a) Acid becomes into the conjugate base
b) Base becomes into the conjugate acid

25
Q

Relationship between the strength of a conjugate acid and a conjugate base

A

The weaker the acid/base, the stronger the conjugate base/acid

26
Q

Amphiprotic definition

A

Substance capable of accepting and donating H+

27
Q

A reaction proceeds to the greater extent in the direction in which…

A

a stronger acid and stronger base form a weaker acid and weaker base

28
Q

Assumptions of weak-acid equilibria problems

A

a) [H3O+] from the autoionization of H2O is negligible
b) A weak acid has a small Ka, so we can neglect the change in its concentration to find its equilibrium concentration

29
Q

% Acid dissociation formula

A

([HA]dis / [HA]i)*100

30
Q

Why does Ka of successive ions differ by several orders of magnitude?

A

It is more difficult for the positively charged H+ ion to leave a singly charged anion than to leave a neutral molecule

31
Q

Factors affecting the acid strength of nonmetal hydrides

A

a) Electronegativity of central nonmetal
b) Strength of the EH bond

32
Q

Polyprotic Acids

A

Acids with more than one ionizable H+

33
Q

Trends of the acid strength of nonmetal hydrides

A

a) Across a period: Increasess
b) Down a group: Increases

34
Q

Factors affecting the acid strength of oxoacids

A

a) Electronegativity of central nonmetal
b) # O atoms around central nonmetals

35
Q

Effect of concentration on the extent of acid dissociation

A

As the initial acid concentration decreases, the percent dissociation of the acid increases

36
Q

Trends of the acid strength of nonmetal hydrides

A

a) Acid strength increases with the electronegativity of nonmetal
b) Acid strength increases with # of O atoms

37
Q

Reasons for the acidity of hydrated metal ions

A

Small and highly charged, which withdraws sufficient e- density from OH bonds of the bound water molecules for an H+ to be released

38
Q

Relationship between Ka and Kb of a Conjugate Acid-Base Pair

A

(Ka)*(Kb) = Kw

39
Q

Acidity of a salt from strong acid and strong base

A

Neutral
(NaCl)

40
Q

Acidity of a salt from strong acid and weak base

A

Acidic
NH4+ + H2O ↔ NH3 + H3O+

41
Q

Acidity of a charged metal cation and anion of strong acid

A

Acidic
Al(H2O)63+ + H2O ↔ Al(H2O)5OH2+ + H3O+

42
Q

Acidity of a salt from strong base and weak acid

A

Basic
NO2− + H2O ↔ HNO2 + OH−

43
Q

Acidity of salts of amphiprotic anions or anions from weak acids / cations from basic cations

A

Depends on Ka and Kb

44
Q

Leveling Effect of Water

A

An acid yields the cation and a base yields the anion that would be produced by autoionization of the solvent.

45
Q

Why are all strong acids and
strong bases equally strong in water?

A

In water, the strongest acid
possible is H3O+ and the strongest base possible is OH−:

46
Q

Method used to rank the relative strength of strong acids

A

Dissolve them in a solvent that is a weaker base than water, so it accepts their protons less readily

47
Q

Lewis acid definition

A

Species that can accept a pair of electrons

48
Q

Lewis base definition

A

Species that can donate a pair of electrons

49
Q

Examples of Lewis Acid compounds

A

e- deficient compounds such as B/Al
Molecules with a polar double bond (e.g. SO2 / CO2)
Metal ion in complex ions

50
Q

Lewis-acid base reaction

A

Donance and acceptance of an e- pair to form an adduct, a single species that contains a new covalent bond

CHM2046 (8 decks)

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